Because of the angular deficit around cosmic string, cold dark matter(CDM) gets the velocity toward the plane of moving string and wake is formed there. It means that CDM body is cut by string, two blocks move each other, and the overlapped region becomes wake. The wake and/or block size is determined by the horizon size at zi when the wake is triggered by the string. The nonlinearity and/or thickness of the wake depends on the moving length of CDM toward the wake which depends on zi, the line density and velocity of string.