Based on a synthesis on the basic principle and the phase measurement method of laser range finder phase-shift system,the problem between range measurement and resolution measurement is solved by a twofold modulation frequency method,meanwhile,the complexity of electrocircuit is diminished by the method of difference frequency for phase measurement.Based on modularization,the basic principle of laser range finder system is first simulated by Matlab,and three principal measurement methods (The frequency digital phase measuring,the digital synchronous demodulation phase measuring,the automatic digital phase measuring) are compared.At last,the feasibility of a new laser range finder phase-shift system including high-resolution and quick reaction performance is proved in theory,a good foundation for achieving actual equipment later is well prepared.