The high cycle fatigue behavior of die casting magnesium alloy AZ91D containing 1% mischmetal (AZ91D-1%MM) at the stress ratio of 0.1 was investigated. The microstructure difference between the skin and the core region of the die casting specimen was analyzed using optical microscopy and XRD. The ultimate tensile strength, yield strength and elongation are 185 MPa, 159 MPa and 1.5% at room temperature, respectively. The p-S-N curve (p=50%) of the die casting AZ91D-1%MM is determined and the fatigue strength at 3.8×105 cycles is 70 MPa. A linear relation between S and Np in log scale between 103 and 106 cycles is given as lgNp=17.85–6.83lgS. The fracture surfaces of some fatigue specimens at lower stress exhibit rubbing mark. The fatigue fracture surface of specimens with minor defects possesses the mixed characteristics of quasi-cleavage and gliding fracture such as tearing ridge, dimple or fatigue striation; therefore, the material belongs to lower-ductility materials.