Abstract: Series of small yield chemical explosion tests, which media were uniform near the explotion sources, were performed in a certain hard rock to investigate the relationship between explosion seismic coupling intensity and yield in the same buried depth. The magnitude spectra of explosion seismic function reduced velocity potential for two chemical explosions which yield ratio was two, were compared with the ground motion data to obtain that the seismic coupling ratio is approximately equal to two. Therefore, it was concluded that underground explosion seismic intensity be directly proportinal to yield in the same explosion depth.