Quantum well intermixing induced by impurity diffusion has been used in fabricating nonabsorbing windows in the cavity facets to improve the output power of high-power laser diodes. A series of experiments on quantum well intermixing induced by Zn impurity diffusion were done on 650 nm laser diode wafers at 550 ℃. Zn was diffused using a closed ampoule method with Zn3As2 as source material. Blue shifts of photoluminescence (PL) spectra taken on the sample increase with the increasing of diffusion time, and the maximum PL blue shift is 53 nm. When the diffusion time was above 60 min, PL red shift occurred with a PL blue shift on the samples and the maximum PL red shift is 32 nm. It is concluded that the PL blue shifts come from the inter-diffusion of Al and Ga atoms between GaInP wells and AlGaInP barrier layers, while the PL red shifts come from the Ga0.51In0.49P buffer layer, and they are both induced by the Zn impurity diffusion into the sample. Additionally, the effects of the diffusion time and temperature on the crystal quality of the sample were studied, and the Al-Ga diffusion coefficient was calculated.