Abstract: With the thermal expansion-metallograph method and the Gleeble-1500D thermal simulator,the 30MnCr22 steel's expansion curve of continual cooling transformation under different cooling velocities is measured,having resulted in the continual cooling transformation curve(CCT curve) of the steel.Also conducted is observation of the metallographic structures of the specimens under different cooling velocities via a ZEISS microscope.And the micro-hardness value of each specimen is measured with a LEICA micro-hardometer.The result of analysis of the CCT curve can be sued as the theoretic basis for establishing heat treatment process for the 30MnCr22 oil casings.