Tongli thoroughly study the basic theory of slewing ring, revealing seven parameters which affect the loading capacity of the ball type slewing ring, including raceway surface hardness, hardening depth, matrix hardness, clearance, clearance difference between upper raceway and lower raceway, curvature ratio and contact angle. The scientific technical index and reliable technological processing double the loading capacity of the slewing ring. Rated static capacity per kg ≥ 20kN, raised by 1-2 times.