In order to explore a performance optimization scheme for germanium laser,firstly,a model of double- heterojunction Fabry-Perot electrically-pumped edge emitting germanium laser is established on the basis of biaxial- ly-tensile strain.Then,the relationship between the biaxially tensile strain and the optimal doping density is dis- cussed with the help of the proposed model.Finally,the variations of such laser parameters as threshold current density and electro-optical conversion efficiency with both biaxially-tensile strain and doping density are analyzed.The results show that ( 1) the optimal doping density decreases as biaxially-tensile strain increases,and,excessive doping may lead to laser performance degradation; ( 2) at the same doping density,both optical gain and peak gain wavelength increase as biaxially-tensile strain increases; and ( 3) in comparison with the literature data,germanium laser with 0. 8% biaxially-tensile strain and with the corresponding optimal doping density ( 8 ×10¹⁹cm^-3 ) posses- ses a threshold current density as low as 1/10 of that of the literature value,while the electro－optical conversion efficiency nearly increases by 10 folds.