The results of crystallization experiments of a granodioritic melt, at conditions of 500 ~2 000 MPa, 650 ~750 ℃ and H2O-unsaturated or-saturated, showed that, at 500 MPa and H2O-saturated, the plagioclases began to crystallize at 675 ℃, and that pressure, temperature and H2O content had obvious impact on the crystallization and composition of plagioclases.The SiO2 contents in residual melt with crystallization of plagioclases were higher than those without the present of plagioclases. Therefore, the preliminary experimental study on the major element compositions suggested that the A-type granitic magma in East Junggar could be derived from the crystallization differentiation of the granodioritic magma in the same region.