The present invention is a sealing structure for a rotary valve of a squirt gun. The rotary valve is placed into a housing of the squirt gun body between an inlet duct and an outlet duct. The rotary valve is provided with a through hole, and both ends of the rotary valve are connected to a button outside of the squirt gun body. The rotation angle of the rotary valve can be adjusted to control the switching or misalignment state between the through hole of the rotary valve and the inlet duct and the outlet duct. A flexible sealer is placed on the outer wall of the rotary valve opposite to the inlet duct or outlet duct of the squirt gun body. When the through hole of the rotary valve is misaligned with the inlet duct and outlet duct, the flexible sealer is placed opposite to the inlet duct or outlet duct to achieve water-tightness, thereby reducing the components and saving the manufacturing cost for improved industrial applications.