Granitic batholith in Xiangjiananshan in the eastern East Kunlun Orogenic Belt presents the distinct features of magma mixing. Plagioclase, as a main rockforming mineral, is an effective tool to study petrogenesis, magma evolution and magma mixing. Petrography and mineral chemistry of plagioclases in host rock and its mafic microgranular enclaves (MMEs) in granitic batholith of Xiangjiananshan were studied through electron microporobe (EMPA). The results show that the plagioclases with oscillatory zonings（39~48，21~36） and plagioclasebearing minerals（29~45，14~32） in host rock and the plagioclases xenocrystals （41~49，35~36，43~49，31~47，27~38）in MMEs have a serial geochemical evolution of anorthitealbite component value (An value), and part of plagioclase core has high An values（59~72） due to late fluid alteration. Most plagioclases in matrix of the MMEs have corerim structures with Anvalue discontinuities from core（52，31）to rim（33~37，25）. Minor plagioclases have lower An values （49）in cores due to alteration, with higher An values in cores（55~71）than in rim（46~49）. In addition, some plagioclases in the matrix are jigsawlike patches, with high An（66）in dark areas and low An（33~39）in light area. The plagioclase xenocrystals in MMEs have been divided into two categories according to mineral contents. The “clean” ones without minerals have apparent oscillatory zonings and polysynthetic twins, and a narrow fluctuated range of Anvalue（41~49，35~36）. Whilst the “dirty” ones with minerals have an unsmooth fluctuation of Anvalues （43~49，31~47，27~38）, with higher Anvalues in some testing points（78）and accretion rim（73）due to alteration. The studies above show that the normal evolutional sequence of plagioclases in the host rock represents the magmatic evolution of the host rocks with the magma evolving from mafic to feslic gradually. After the MMEs entered the host rock, the plagioclases in the MMEs would be eroded and crystallized due to decreasing of temperature, pressure and water saturation. Plagioclases xenocrystals in enclaves, which originated from host rock, vary in composition and structure due to change in temperature and pressure as well as growth at the late stage. The complex oscillatory zonings of plagioclases in granitic batholith of Xiangjiananshan and their MMEs are the results of injection of mantlederived mafic magma into felsic magma.