An improved binary amplitude modulation-based phase retrieval method studied by means of simulations and experiments is presented in this paper. The idea of ptychography is introduced for the purpose of designing random binary amplitude masks. The masks have the features that part of the light transmission regions is overlapped with each other and the overlapping positions are randomly distributed. The requirement for the consistency of light field in overlapping regions forms a strong constraint which is similar to the overlap constraint in ptychography. The constraint makes the iterative algorithm have high convergence accuracy in comparison to that of the original binary amplitude modulation method. Influences of amounts and overlap ratio of the modulation mask on reconstruction accuracy and speed of imaging process are analyzed. The comparison between our method and the original binary amplitude modulation method is performed in order to verify the feasibility of the proposed method.