This work presents digital retrodirective method to do microwave power transfer (MPT) for solar power satellite (SPS). Due to space environment, there is concern of antenna deformation, which will affect beam forming. Size of SPS is large and synchronization among antenna modules is difficult. Flexibility regarding frequency selection for MPT is also a requirement for SPS. Digital Retrodirective method determines phase of pilot signal and power signal is transmitted with conjugate phase. Digital Signal Processing (DSP) circuit is used for digital retrodirective method. Experiment is performed without antenna deformation and with antenna deformation cases. Digital retrodirective method performs beam forming without synchronization among antenna modules and corrects effect of antenna deformation successfully. Flexibility for frequency selection is also achieved by the DSP circuit. The presented results confirm that digital retrodirective method is a good candidate for power transfer from SPS.