Recently, I've been thinking about the KDJ indicator and realized that many people aren't using it deeply enough.

Let's first talk about the composition of this indicator. Among the three lines of KDJ, the J line fluctuates the most frequently, the K line is next, and the D line is the most stable. Its core logic studies the relationship between the highest price, lowest price, and closing price, while also integrating momentum concepts, strength indicators, and moving averages. This is why it can quickly and intuitively assess market trends, making it one of the most commonly used technical analysis tools in futures and stock markets.

In terms of sensitivity, the J value is the strongest, the K value is next, and the D value is the slowest. But in terms of safety, the J value is the worst, the K value is next, and the D value is the most stable. This trade-off is very important and determines how you use this indicator.

Regarding practical application, KDJ indeed has a good grasp of short- and medium-term trend analysis. The weekly-level KDJ indicator provides especially useful guidance for medium-term trading. The basic logic is clear: when the weekly J line heads upward below zero and a weekly bullish K line closes, it's a buying opportunity. But if the stock price is in a bear market below the 60-week moving average, the J line will flatten below zero—don't rush to buy; wait until the J line turns upward and a weekly bullish candle closes. Conversely, when the weekly J line rises above 100, turns downward, and a weekly bearish candle closes, be alert for a top and consider reducing positions.

However, there's a point many overlook—the optimal parameters for the KDJ indicator are not actually the default system setting of 9. Based on my experience, using 9 on daily charts results in too many fluctuations, signals, and noise, which is why many people feel this indicator is useless. But if you adjust the parameters, the effect can be completely different. From practical experience, parameters like 5, 19, and 25 work quite well. You can flexibly set them based on different stocks and timeframes.

Regarding overbought and oversold conditions, a D% greater than 80 indicates overbought, less than 0 indicates oversold. A J% greater than 100 indicates overbought, less than 10 indicates oversold. When K% crosses above D% (a golden cross), it's a buy signal; when it drops below D% (a death cross), it's a sell signal.

But I must say, the KDJ also has flaws in actual use. When the K value enters overbought or oversold zones, it often becomes dull, making it hard to interpret. During short-term volatile price movements, using KD cross signals to buy or sell can lead to buying at the top and selling at the bottom. Moreover, this indicator is especially suitable for ranging markets; once the market enters a trending phase—either up or down—it tends to fail.

The most noteworthy signals are from the J value. When the J value exceeds 100, especially if it stays above 100 for three consecutive days, the stock price often shows a short-term top. When the J value drops below 0, especially if it stays below 0 for three days in a row, the stock price often shows a short-term bottom. These signals are rare but highly reliable once they appear. Many experienced traders specifically watch J value signals to grasp the best entry and exit points—this can be considered the essence of the KDJ indicator.

In summary, KDJ is a short-term tool suitable for analyzing shorter cycles. For longer-term analysis, use the weekly KDJ. And remember, this indicator works best in ranging markets; don't rely on it during strong trending phases.