Two different frequencies (1 kHz and 15 kHz) of medium-wave infrared lasers were used to compare the interference effect at a distance (15 km) to the same target, the relationship between laser frequency and interference effect was analyzed, and the laser power density reaching the detector was calculated. The experimental results show that the interference effect of the medium-wave laser with high repetition frequency (15 kHz) is obviously better than that of the medium-wave laser with low repetition frequency (1 kHz) when the laser wavelength and average power are the same. The experimental results have certain guiding significance for the development of photoelectric countermeasure equipment.