To eliminate the residual polarization sensitivity of arrayed waveguide grating (AWG) embedded with a half- wave plate, a strategy using optically asymmetrical slab waveguides is proposed. An improved transfer function is given to analyze the polarization mode conversion process with a half-wave plate embedded in AWG. For the exemplary case that the half-wave plate is not embedded in the middle of AWG due to fabrication errors, the thermo-optic effect is utilized to adjust the birefringence of the slab waveguides to realize optical asymmetry of them, and the residual polarization sensitivity is eliminated. For the polymer AWG, the simulation results show that when the temperature difference between the input and output slab waveguides is 24 ° C, the residual polarization sensitivity of 32.43 pm can be eliminated. Further the research reveals that the AWG center wavelength drifting can be avoided when the temperature difference of the input and output slab waveguides is equal but with an opposite sign. The proposed method has advantages, such as simple structure and adjustable temperature control, and can also be useful to eliminate the residual polarization sensitivity caused by other factors associated with embedded half-wave plate.