The crushing cavity of symons cone crusher consists of the moving cone and the fixed cone. The moving cone is installed on the upper of the main shaft under pressure, while one end of the main shaft is inserted into the conical hole of the eccentric bush. The conical hole of the eccentric shaft bush is internally equipped with the bronze bush or nylon bush. When the transmission gear drives the eccentric shaft bush, the main shaft inserted into the eccentric shaft bush drives the moving cone to keep cycloidal rotation so that the space between the mantle and concave will regularly reduce and increase to squeeze materials and discharge the final crushed materials.