Numerical simulations have been done for a compressible mixing layer, in which the inflow speed on the low speed side was made to have periodic undulations, so as to see if this method could enhance the mixing effect of the layer. Systematic computations for a 2-D compressible mixing layer with Mach number M e = 0.6 have been done, and the results showed that the proposed method was indeed effective in enhancing the mixing.