A mixed-mode I-II fracture fixture and modified compact tensile specimen are designed to investigate mixed-mode I-II fracture behavior of FV520 B stainless steel used in centrifugal compressor impeller. The results show that this mixed-mode fracture belonged to micro-porous coalescence ductile fracture mechanism. With loading angle increasing,some dimples on the fracture surface were slightly stretched along the crack propagation direction and became shallow,which was caused by the increasing shear component of stress. As the loading angle increased,total fracture toughness increased,of which the values at loading angles of 22. 5 ° and 45 ° were 1. 8 and 4. 4 times higher than that under pure I mode,respectively,moreover,both mode I and mode II components of the total fracture toughness,and the crack initiation angle increased,which could be well predicted by using mixed-mode J integral fracture criterion. This study can provide some insight into mixed-mode fracture analysis of centrifugal compressor impeller.