To improve of polarization of master oscillator power amplifier (MOPA), the factors which have impact on the polarization characteristics of ridge and tapered waveguides are studied. The optical confinement factor of TE-mode in ridge waveguide is enlarged by 1.35 μm deep etching, whereas the TE optical gain in tapered amplifier is improved through on-chip metal stress regulation. Combining the methods above, the degree of polarization (DOP) of two section are prominently enhanced in addition to reduced polarization angle difference. Finally, a 90% DOP of the MOPA has been achieved by standard process fabrication.