Abstract: Dry sliding wear tests were performed for 3Cr3Mo2V cast steel and 3Cr13 steel at 25 ℃ and 200 ℃ on a pin-on-disk wear tester.The effect of microstructures and tribo-oxides on the wear behavior of 3Cr3Mo2V cast steel and 3Cr13 steel was probed into and the wear mechanism was also discussed.The results show that tribo-oxides exert a significant influence on wear behavior and mechanism,and the wear reducing effect of tribo-oxides depends on their amount and substrate state that is closely related with the compositions and microstructures of the steel.High Cr content impedes the formation of tribo-oxides and tempered sorbite with low hardness accelerates the stripping of tribo-oxides,thus,the wear reducing effect of tribo-oxides is destroyed or reduced.