Abstract: In this paper, the first approximation solutions of the incompressible plane turbulent mixing layer using the theories of Chou Peiyuanhave been given. We consi-der the continuity equation, the mean motion equations and the equations of the double velocity correlations, and ignore the triple velocity correlations of the double velocity correlation equations. We introduce the hypothesis of the self-preservation, and have gotten the theoretical results of the mean velocities, the double velocity correlations a...