Abstract: The main characteristics of seismic source function in underground explosion are studied by seismological method and numerical method. Especially, the influence of water content on seismic source function is studied, and it reveals that the coupling energy of underground explosion increases with the increase of the water content. The steady-state value of RDP in water-saturated granite is higher than that in dry granite, and correspondingly, the value increases with the increase of water content. However, the corner frequency of RVPs amplitude spectrum of water-saturated granite is lower than that in dry granite, and its value decreases with the increase of water content. The asymptotic behavior of RVP at high frequencies, or roll-off, is thought to be steeper than f-2. The overshoot of RDP at the far-field is not obvious.