Hypothesis the beam signal model of laser heterodyne detection system is Gaussian local-oscillator beam and Airy spot signal beam in this context. With this physical model, analysis in detail a particular additional consumption gene in heterodyne detection heterodyne efficiency. Establishing their math model, discussion the surface curve including non-collimation influence of numerical value simulation, swing distributing of optic field, non-matching angle of dimensional and local-oscillator light, etc, affect the degree of heterodyne efficiency, and that the main factors can cause heterodyne efficiency to decline are non-collimation influence of numerical value simulation and non -matching angle of dimensional. So, controlling the beam parameter is put forward, and non-collimation difficulty of laser heterodyne optic system is declined. In ideal status, the upper limit of heterodyne efficiency of Gauss local-oscillator and Aiiy spot signal is 0.82.