A water spray gun, comprising: a) a gun body, the gun body comprising: a water passage and double water hole disposed therein; b) a valve switch; and c) a device for switching a spray pattern, the device comprising a water spray cap, a water spray plate, a decentered interface, a second spring, a wedge rotating piece for water diversion comprising a plurality of negative wedge blocks each comprising a negative wedge, a wedge push rod comprising a plurality of positive wedge blocks each comprising a positive wedge, a housing of a gun head, and a trigger, all of which being successively mounted on an upper part of the gun body; wherein the trigger is movably disposed at a middle part of the gun body for controlling the device for switching the spray pattern; and when a lower part of the trigger is pressed, an upper part of the trigger pushes the wedge push rod; the positive wedge of each positive wedge block disposed on the wedge push rod interacts with the negative wedge of each negative wedge block disposed at the wedge rotating piece for water diversion so as to drive the wedge rotating piece for water diversion to rotate; the water spray cap is driven by the wedge rotating piece for water diversion to rotate thereby realizing the switch of the water diversion; characterized in that the valve switch comprises a button, a pressing piece comprising a unilaterally oblique plane, a rear plate comprising an inner guide rail, a rotating piece comprising a unilaterally oblique plane, a first spring, a front sealing ring, a switch rotating core, and a double sealing ring, all of which are successively mounted at an upper rear part of the gun body; the button is movably disposed on the upper rear part of the gun body for controlling the valve switch to close or open the water passage; a water flowing state and a water stopping state of the valve switch are switched by pressing and releasing the button once; when the button is pressed, the pressing piece is driven by the inner guide rail of the rear plate to move merely in a pressing direction while the rotating piece is driven by the unilaterally oblique plane of the pressing piece to rotate; and the switch rotating core is driven by the rotating piece to close or open the double water hole disposed inside the gun body to control the water flow in the water passage whereby realizing the valve switch between the water flowing state and the water stopping state; and the trigger functions as a lever via a pin as a fulcrum. a) a gun body, the gun body comprising: a water passage and double water hole disposed therein; b) a valve switch; and c) a device for switching a spray pattern, the device comprising a water spray cap, a water spray plate, a decentered interface, a second spring, a wedge rotating piece for water diversion comprising a plurality of negative wedge blocks each comprising a negative wedge, a wedge push rod comprising a plurality of positive wedge blocks each comprising a positive wedge, a housing of a gun head, and a trigger, all of which being successively mounted on an upper part of the gun body; the trigger is movably disposed at a middle part of the gun body for controlling the device for switching the spray pattern; and when a lower part of the trigger is pressed, an upper part of the trigger pushes the wedge push rod; the positive wedge of each positive wedge block disposed on the wedge push rod interacts with the negative wedge of each negative wedge block disposed at the wedge rotating piece for water diversion so as to drive the wedge rotating piece for water diversion to rotate; the water spray cap is driven by the wedge rotating piece for water diversion to rotate thereby realizing the switch of the water diversion; the valve switch comprises a button, a pressing piece comprising a unilaterally oblique plane, a rear plate comprising an inner guide rail, a rotating piece comprising a unilaterally oblique plane, a first spring, a front sealing ring, a switch rotating core, and a double sealing ring, all of which are successively mounted at an upper rear part of the gun body; the button is movably disposed on the upper rear part of the gun body for controlling the valve switch to close or open the water passage; a water flowing state and a water stopping state of the valve switch are switched by pressing and releasing the button once; when the button is pressed, the pressing piece is driven by the inner guide rail of the rear plate to move merely in a pressing direction while the rotating piece is driven by the unilaterally oblique plane of the pressing piece to rotate; and the switch rotating core is driven by the rotating piece to close or open the double water hole disposed inside the gun body to control the water flow in the water passage whereby realizing the valve switch between the water flowing state and the water stopping state; and the trigger functions as a lever via a pin as a fulcrum.