Abstract: The P-wave first motion solutions are given in this paper for 70 shocks of magnitude equal to and greater than 4 which occurred in Southwestern China and adjacent areas during 1973—1979. The relative motion of intraplate blocks including the Yun-nan-Xikang rhombic block,Sichuan-Qinghai block,and the Southwestern Yunnan block is studied on the basis of the focal mechanism,seismic fissures,horizontal deformation in the seismic areas and the trend of variations of the length of baselines across major faults.The direction of the lateral motion of crustal material of three blocks in question is SE-SSE.The Yunnan-Xikang rhombic block can be devided into several sub-blocks and their relative motion is also discussed in this paper.