Abstract: Studied in the paper is the quenching & tem pering process for the experimental 25CrMoBVRE steel which is a non-API BT100H steel for the oil casing as serving in the heavy oil thermal recovery well,involving analysis of microstructures and properties thereof as indicated on the conditions of specific quenching and tempering processes. As a result the facts as follows are revealed. The after-quenching microstructure of the 25CrMoBVRE steel is of the lath martensite,and along with increase of the quenching temperature,the distribution homogeneity of the lath martensite is increased too,meanwhile the grain size of the primary austenite is getting enlarged gradually. And along with rising up of the tempering temperature,the strength of the specimen is reduced,whereas both plasticity and toughness of it are improved obviously;owing to the extension of the tempering-holding duration,the yield strength and tensile strength of the specimen are so slightly reduced,while the elongation rate and the impact energy are so little changed;due to rising up of the tempering temperature or the extension of the holding duration,the granular carbides are distributed in the crystal boundary and in the crystal itself,while the grain is returning to its original form,i.e. the equiaxial grain.