Real-time algorithms are given to generate 4-channel stereo sound for virtual battlefield. For the special case of 4-channel stereo sound, first we studied the speaker layout scheme of 4-channel stereo sound system. Based on the given speaker layout, we dealt with the attenuation of sound intensity and turned a mono sound into a stereo one. Then, a criterion for evaluating the effect of sound mixing is proposed. An algorithm based on this criterion is also given to mix sounds randomly in real-time. The algorithm has been successfully applied in one of our applications to realize a real-time 4-Channel Stereo Sound environment for virtual battlefield. The effect is quite good.