The transport of intensity equation is solved to recover the phase information through the combination of optics and calculation in the method of phase retrieval based on the intensity measurement.This method is proved to be a feasible way to obtain phase information theoretically and experimentally.A new derivation of Green function method in Neumann and Dirichlet boundary conditions is deduced.Because the partial derivative of Green's function is a four-dimensional matrix

large memory space will be occupied with the improvement of image resolution by solving the function directly.The numerical processing method is presented and extended to natural light conditions.At same time

an optical data collection platform is built.Simulation and actual experimental results verify this new phase retrieval method is reasonable and correct.