The invention discloses a piston. The piston comprises a head part on the upper portion and a skirt part on the lower portion, wherein the head part and the skirt part are integrally formed. A combustion chamber is arranged on the upper end of the head part. A cooling oil cavity is formed in the lower end of the head part. The cooling oil cavity is arranged annularly. An oil inlet port and an oil outlet port are formed in a separating wall between the cooling oil cavity and the skirt part. Two facing windows are left and right symmetrically arranged on the skirt part. Pin holes with horizontal axes are formed between the two facing windows in a penetrating mode. The pin holes are used for being connected with a peripheral piston pin, wherein the inner cavity height of the position, where the diameter direction of the cooling oil cavity is perpendicular to the axis of the pin holes, of the cooling oil cavity is d1, the inner cavity height of the position, where the diameter of the cooling oil cavity is parallel to the axes of the pin holes, of the cooling oil cavity is d2, the inner cavity height d1 of the cooling oil cavity is less than d2, and the inner cavity height is gradually increased from d1 to d2. The invention further provides a manufacturing method for the piston. According to the piston and the manufacturing method thereof, the phenomenon that the piston is prone to cracking and losing efficacy due to poor structure density of a cast steel piston is effectively reduced, and the using performance of the piston is improved.