Under the principle that the arrival time difference of P wave of the 2 earthquakes with the same locations recorded by the same station is a constant，the paper found the aftershocks near the Wenchuan earthquake，and with the advantage of close distance to the epicenter with clear and complete recorded waveforms，determined the epicenter and origin time of the quake: the position of 31. 049°N，103. 338°E，the depth of 6. 0km，and origin time ( Beijing time) of May 12，2008，14: 27: 58. 79．