Abstract: As expand of cities and intension of human activities,earthquake monitoring has become more and more disturbed by the environmental noise.This interfere the determination of earthquake parameters and other geophysical phenomenon study.Based on the seismic wave data of Wenchuan earthquake on May 12,2008 recorded by the Fangzai seismic station at the high environmental noise,we present the method of how to extract the effective seismic wave signal from the strong environment noise by means of the digital signal processing.Based on the direction of the azimuth angle and the emergence angle,we recombine the signal of 3 components of the seismic wave record to identify the first arrivals of seismic wave.Finally,we summarize the general process of extracting the effective seismic signal.