Abstract: By means of theoretical and experimental methods,the stationary and directional feature of ground mic-rotremor signals is presented. The relationship between the microtremor spectrum and the ground response spectrumis also studied. Based On these,a method of detennining the natural frequencies of soil deposit is suggested,accord-ing to the peak frequencies of the microtremors.The proposed method can readily be used on the ground surfacewithout drilling any boreholes,therefore,it is an economical and attractive way for engineering exploration .