Abstract: Since 1905 A. D., the Huichun deep seismic belt and the tectonic earthquakes in the northeast continent have undergone three stages of synchronous activity. Based upon the synthetical analysis of the mantle convection in the deep seismic zone and the focal meehanism, it is consi dered that the thrust faulting appeared at the plate of the west Pacificafter the plate inserted into the Huichun upper-mantle at depth of 590km and with a dip of 27 degrees from east to west, which resulted in the uplift of inland upper-mantle and therefore caused the tectonic seismic activity in the crust with its direction from east to west in space and synchronous activity in time.