In order to reveal the magma mixing mechanism of the Mid-late Triassic Jiefangyingzi Pluton on the northern margin of the North China Craton, this paper carried out electron microprobe analyses of plagioclase and hornblende in host rock and mafic enclaves. The results show that the plagioclase phenocrysts in rich-phenocrysts enclaves and the edges of poor-phenocrysts enclaves develop the spike zone of increased An value. The spike zone of An value (32~46) is higher than those of the core and rim in same plagioclase grain, and the An value of the core is consistent with that of plagioclase in host rock, indicating the spike zone was the result of the mafic magma capturing and modifying the plagioclase from host rock. The core of plagioclase at the central part of poor-phenocrysts enclaves has an erosion sieve structure, and the An value of the residual part (40~47) is higher than that of the erosion part (32~36) in the core of the plagioclase grain, but generally higher than that of rim in the phenocryst and fine-grained plagioclase in the matrix (17~35), indicating the central part of the enclaves has been modified by felsic composition. On the other hand, the TiO₂ content of hornblende phenocrysts in host rocks (0.50%~1.10%) is significantly lower than that of hornblende in enclaves (1.17%~2.47%), while the TiO₂ content of fine-grained hornblende in the matrix (1.58%~2.26%) is similar to that of hornblende in enclave, indicating that there was a mixture of mafic components at the late stage of host rocks evolution. The above studies show that magma mingling on a macroscopic scale and the migration of minerals and elements of magma mixing on a microscopic scale occurred between mafic and felsic magma during the formation of Jiefangyingzi Pluton.