The p-waveguide thickness which maximizes the power conversion efficiency (PCE) is optimized for quantum well diode lasers. The optimization are based on the simple models of the semiconductor laser′s electrical and optical behaviors,including series resistance,threshold current and internal loss. The structure is designed and the device is fabricated experimentally. For a 1500 μm cavity length and 20% fill factor devices,the threshold current and series resistance are 7.3 A and 4.8 mΩ respectively,and a low internal loss around 0.78 cm－1 is achieved. Under continuous wave operation condition,the maximal electro-optical conversion efficiency of the standard 1 cm laser bar with micro-channel cooler is 63.2%. The corresponding slope efficiency and output power are 1.17 W/A and 36.2 W. The maximal output power is 139.6 W when the current is 161 A. The results prove that the way through optimizing the p-waveguide thickness is an efficient approach to improve.