Xiaerpu granite is composed of host rock, mafic microgranular enclaves and intermediate-basic dyke swarms, with the development of abundant and typical petrographical evidence of magma mixing. In field outcrops, dark minerals are distributed asymmetrically, and dark mineral aggregates, mafic microgranular enclaves, bands of nonuniform mixing are well developed. Mafic microgranular enclaves show characteristics of strong plastic distortion and clear boundary or transitional relationships with host rocks, with well developed reversed veins and captured feldspar phenocrysts (captured crystals). These phenomena suggest that mafic microgranular enclaves and basic dyke swarms might have originated from basic magma formed at the same time as the host rock, and they probably experienced strong magma mixing. Petrographic features provide important evidence for magma mixing of Xiaerpu granite.