To solve the high Bit Error Rate (BER) caused by rate oscillation in traditional Data Rate Change (DRC) algorithm, an improved DRC algorithm based on Adaptive Frame Length (AFL) was proposed for short-wave communication. Firstly, in the initialization phase, the frame length and transmission rate of the initial transmission were determined by the parameters of the current channel and the information of previous empirical values, and the data transmission was started. Then, if two frames with the same length were successively sent in the transmission process, the frame length would be accordingly increased. If the retransmission failed twice in a row, the frame length would be halved in the next transmission. Finally, the frame error rate was calculated based on the current frame length. The data rate would be increased if the value was less than the preset threshold. Compared with RapidM DRC, the average link BER of the proposed algorithm was decreased by 1.8 percentage points, and the link availability was increased by 11 percentage points. Experimental results show that the proposed algorithm can eliminate the rate oscillation and improve the communication capability of the short-wave communication system.