The work aims to explore the process effects of circular plasma nitriding and conventional constant temperature plasma nitriding technology. Firstly, the specimen quenching and tempering was carried out. Plasma nitriding was conducted by groups. The flows of ammonia and ethanol were fixed. The two technological parameters (nitriding time and nitriding temperature) and nitriding technology were changed to respectively measure the surface hardness and nitriding thickness of each specimen after nitriding. The metallographic structure of each specimen was observed and the nitrided layer performance of each group of specimens was analyzed. The surface hardness of circular plasma nitrided 530 ℃ 6 h specimen was the highest. With the increase in the nitriding temperature and the prolonged nitriding time, the surface hardness of specimens was increased. However, when the temperature exceeded 530 ℃ and the time was over 6 h, the surface hardness of specimens would be reduced instead. The nitrdied layer thickness of the circularly nitrided 550 ℃ 10 h specimens was the maximum. With the increase in nitriding temperature and nitrding time, the nitrided layer of the specimen would become thicker. However, when the time exceeded 6 h, the nitriding thickness was increased more slowly. The nitriding thicknesses at 6 h, 8 h and 10 h were of little difference. At the same nitriding temperature, the nitrding thickness of specimen circularly nitrdied for 6 h was basically the same with that of the specimen subject to 10 h conventional constant temperature nitriding. Within the same nitriding time, the surface hardness of the circularly nitrided specimen at 510 ℃ was higher than that of the nitrided specimens at the constant temperature 550 ℃, and both nitriding thicknesses were almost the same. Circular plasma nitriding technology is superior to the conventional constant temperature plasma nitriding and the circular plasma nitrided 550 ℃×8 h specimens have the best overall performance.