Lower rotary platform which is above leg support of circular stockyard stacker is basic unit of rotary to upper stacker and lower stacker. The lower rotary platform is main unit in bearing weight and support weight and dynamic loading of device when circular stockyard stacker is working,so its quality is very strict in welding. In this paper,reasonable welding technology method of quality control for main unit is summed up according to feature of structure of central rotary platform in circular stockyard stacker. Practice has proved that the reasonable welding technology may control effectively deformation of welding and ensure quality of welding,thus laying the foundation for the safe use of the whole machine.