The application discloses an all-steel piston. The all-steel piston comprises a piston main body, wherein a groove is formed in the piston main body; and a cover plate is welded on the piston main body by high-energy beam and is used for blocking an opening of the groove so as to seal an inner cooling oil cavity. According to the all-steel piston provided by the invention, the open processing of the inner cooling oil cavity can be carried out on the piston main body, and the inner cooling oil cavity is then sealed through connecting the cover plate, so that the inner molding processing of the inner cooling oil cavity is avoided, and accordingly, the processing difficulty of the inner cooling oil cavity is lowered; the cover plate and the piston main body are connected in a high-energy beam welding manner rather than connected by a bolt, a nut and a piston pin, so that the intensity of the piston structure is ensured, and the risk of multi-workpiece connecting failure is avoided; and meanwhile, the mode of friction welding is no longer used, a hemming is also prevented from occurring in the inner cooling oil cavity, the circulation cooling effect of cooling oil in the inner cooling oil cavity is enhanced, and the quality and the work effect of the all-steel piston are obliviously improved.