Abstract: The photonic laser propulsion is a new propulsion concept, which uses the thrust amplification generated by multiple momentum exchange and photon energy recycling through photon oscillation in external cavity composed of two HR mirrors. The experimental study and results related to photonic laser propulsion based on oscillation in external cavity of Gray and Edwards were analyzed. The principle of thrust amplification was introduced; the thrust calculated equations were deduced; the thruster simulation model was built. Finally, COMSOL was used to study and analyze the oscillation cavity's parameters'(cavity mirrors' distance, curvature radius, diameter, relative angle and aperture position) impact on thrust amplification by ray trace method, providing the establishment of future experiments with design basis and theory guidance. The simulation results indicate that in condition of 1 000 W and reflectivity 0.999, the maximum amplification factor 61 and maximum photon thrust 409 N can be realized, satisfying the needs of space missions.