The impact of center waveguide layers, mode expansion layers and confinement layers on semiconductor laser performance with mode expansion layers has been investigated using the crosslight software. A structure with stripe width of 50 μm and far field divergence angle of 23° is obtained, whose threshold current is 117.8 mA and confinement factor is 2.37%. The far field divergence angle can be as low as 18° when the threshold current is 200.9 mA. After optimization the far field vertical divergence angle is reduced by about 20° without obvious threshold current increas. The results show that the mode expansion layers do not reduce the electrical properties and the temperature stability characteristics of lasers.