Abstract: With the aid of X-ray diffraction and hardness tests, hardened circular blades under different tempering processes were tested along the radius in order to determine the distribution and decline of residual stress, including the Rockwell hardness and micro-hardness tests. The results were as follows:① the hardness of hardened circular blades declined rapidly at the early stage of the tempering process; the quenching residual stress also decreased quickly at the same time; changes were slow after a certain amount of time had passed so it had no influence on the steady, long run tempering temperature. ② the decline in residual stress was little affected by cooling in the well distributed cooling process. A new heat stress did not emerge.