The alternate direction implicit (ADI) scheme is introduced to the vector parabolic equation (PE) method for electromagnetic scattering problems. Nonhomogeneous boundary conditions are added on the surface of the scatterer and modification is introduced to the divergence-free condition. A marching solution is used along the paraxial direction and the fields in each marching plane can be calculated line by line in parallel. In this way, a three dimensional electromagnetic scattering problem can be converted into a series of one dimensional problems to be solved. Fewer computing resources are needed with encouraging accuracy when compared with the traditional Crank-Nicolson (CN) scheme. The complete bistatic radar cross section (RCS) can be obtained by the rotating PE method. Numerical results are given to demonstrate the validity, stability and efficiency of the proposed method, and the parallel efficiency is given at the same time.