Abstract: In this paper,the effect of the variation of the wind speed at the top of PBL (the wind direction maintains a constant) on the inner parameters u*/A(the ratio of friction velocity to the wind speed at the top of PBL) and a(the angle between the wind direction near the ground and the wind direction at the top of PBL) are studied by means of the numerical solution of the motion equation in PBL.The wind speeds at the top of PBL increase and decrease as an exponential function of time and approach constant values.In the case of barotropic condition,the values of u*/A and a are taken the form of attenuated fluctuation and approach the values corresponding to the stationary solutions.At any time during the temporal variation process the values of inner parameters are different from that derived from the stationary solutions of PBL equations in which the value of A at that instant is taken as the upper boundary condition.Strictly,the inner parameters derived from the stationary condition should not applied directly to the case of nonstationary condition of wind speed at the top of PBL.The effects of the nonstationary process to the wind profiles are also discussed.