Xiaerpu granite is a typical magma mixing granite in West Junggar Basin. Although petrographical feature provide a important proof for magma mixing, but the double diffusion and relativity of petrochemistry are one of the most effective means of differentiate magma mixing. Petrochemistry feature of mafic microgranular enclave is similar to the host rock, showing strong double diffusion. Magma mixing information from petrochemistry is in conformity with petrographical feature, which support magma mixing, and providing a important proof of magma mixing from another field.