A water spray gun, including: a gun body, a valve switch, and a device for switching a spray pattern. The gun body includes: a water passage and double water hole. The valve switch includes: a button, a pressing piece including a unilaterally oblique plane, a rear plate including an inner guide rail, a rotating piece including a unilaterally oblique plane, a first spring, a front sealing ring, a switch rotating core, and a double sealing ring. The device for switching a spray pattern includes a water spray cap, a water spray plate, a decentered interface, a second spring, a wedge rotating piece for water diversion including a plurality of negative wedge blocks each including a negative wedge, a wedge push rod including a plurality of positive wedge blocks each including a positive wedge, a housing of a gun head, and a trigger.