Abstract: Presented here in the essay are the results of observation and analysis of the metallographic structures of the Cr-Mo series steel pipes as tempered at different temperatures via the X-ray diffraction technique.And studied is the relationship between the tempering temperature and relevant factors namely,dislocation density,yield strength and impact toughness of the steel pipe.Finally,quantitatively investigated are certain elements concerning the pipes as quenched and tempered such as the inner stress and the phase transformation as from the ambient temperature to the elevated.