Abstract: The birefringent double frequency laser is a newly developed laser,its difference of frequencies is wider than convention double frequency laser,up to hundreds mophertz.It is important toselect proper frequency stabilization methonology, and the frequency stabilization methods suffer fromthe effecting of the gain curve properties.In this paper,the analysis on the characteristics of gain curveof a inside birefringent double frequency He-Ne laser is presented. Selecting the ratio Ne20:Ne22 canchange the gain curve.In terms of the experiments and calculating,the optimum ratio of Ne20:Ne22 is 53:47,and the gain curve has beter symmetry,the peak point of the curve can be selected to be the frequency control operation point.