Abstract: Based on observation of microstructure,the effect of thermal processing temperature on the microstructure and property of molded/casting 10CrNi3MoV steels and the relationship between them were investigated.The results showed that for the casting steels,when the thermal processing temperature is 960℃ and over,the grain becomes coarsened and the fraction of granular bainite increased so the strength is ascended and the low temperature toughness is evidently declined.when the thermal processing temperature is below 1000℃,the grain size held ultimately and the fraction of granular bainite is less,so the strength and low temperature toughness is kept on a great level.