Recently, some friends have asked me how to use the KDJ indicator, so I decided to organize and share my experiences and lessons learned over the years.

Honestly, the KDJ indicator is quite useful in the stock market, but it’s also one of the tools most easily exploited by major players to trap retail investors. I used to follow the textbook blindly at first, but later I realized that just watching for golden crosses and death crosses is far from enough.

Let’s start with the basic logic of KDJ. This indicator originally comes from the futures market and was later widely applied to stocks. Its core idea is to analyze the price fluctuations within a certain period by calculating the highest price, lowest price, and closing price to determine whether a stock is overbought or oversold. Simply put, it’s a oscillating indicator used for bottom-fishing and top-selling. The default period is 9 days, but you can adjust it yourself.

In terms of its structure, the KDJ consists of three lines: the fast line, the slow line, and the signal line. The most common trading signals are buying when a golden cross occurs and selling when a death cross appears. But this relies on a key premise: paying attention to the KDJ values within certain ranges. Between 0 and 100, 50 is the dividing line—above 50 indicates a bullish trend, below 50 indicates a bearish trend. An overbought zone is above 80, an oversold zone is below 20, and the area between 20 and 80 is consolidation.

In my practical experience, the most useful techniques are observing divergences and multiple crossovers. For example, if the stock price hits a new high but the KDJ does not, that’s a bearish divergence and a strong sell signal. Conversely, if the stock hits a new low but the indicator doesn’t, that’s a bullish divergence and a buy signal. Once I saw Gusheng Financial Holding with the KDJ dropping below 20 and a golden cross forming, with the J value dropping below zero, I bought immediately, and it later surged 100%.

Another often overlooked aspect is the power of secondary crossovers. A single golden cross might just be a rebound, but if two golden crosses occur near the 20 level, that’s a confirmed bullish signal suitable for medium- to long-term holding. Conversely, two death crosses near the 80 level suggest avoiding risk. I saw this in Gree Electric, where two death crosses appeared at a high level along with divergence, and the stock indeed shifted from an uptrend to a downtrend.

Be cautious of a trap in the KDJ indicator: the dulling at extreme high or low levels. Sometimes, in very strong or very weak markets, the KDJ can become ineffective and fail to move. During such times, don’t rush into trades. I once tried to bottom-fish during a dull phase at a low point, but ended up buying halfway up the move. The correct approach is to wait until the dulling phase passes and clear golden or death cross signals appear before acting.

Another tip is combining multiple timeframes. For short-term trading, I look at the KDJ on 60-minute, 30-minute, and intraday charts. For example, if the 60-minute chart shows a golden cross, then the 30-minute also shows a golden cross but starts to decline, and finally the intraday chart shows a high-level death cross, that’s a relatively high point to sell that day. For medium- to long-term investors, it’s better to combine daily, weekly, and monthly KDJ signals, looking for stocks where all three timeframes show golden crosses, then doing short-term swings on those stocks.

However, KDJ also has clear limitations. It’s most unreliable with stocks that have very low trading volume, such as obscure stocks or newly listed small caps. The accuracy drops significantly. Also, be wary of manipulation by major players. Some institutions exploit the sensitivity of KDJ to shake out weak hands by quickly pushing down the price to create a death cross, then after retail investors sell off, they rapidly rally the stock again. In such cases, it’s best to combine trendlines for judgment—if the stock price remains above the trendline, it’s likely just a shakeout.

Overall, the KDJ indicator is indeed a powerful tool for short-term trading, but the key is to understand its principles and know when to use or avoid it. Don’t blindly chase perfect buy or sell points; sometimes, having a margin of safety is more important than pinpoint accuracy.