The invention provides a plastic spraying gun beneficial to uniform liquifying of plastic powder. The plastic spraying gun comprises a plastic spraying gun main body, a plastic powder storage bottle, a powder gas mixing auxiliary mechanism, a gas supply mechanism and a flame holder. The plastic spraying gun main body comprises a gun barrel and a gun handle. The gun barrel is provided with a flammable gas guiding and conveying channel, a powder-gas mixed guiding and conveying channel and a liquid storage cavity. The flammable gas guiding and conveying channel communicates with the powder gas mixing guiding and conveying channel. The plastic powder storage bottle is detachably mounted on the gun barrel. The powder gas mixing auxiliary mechanism comprises a first communicating pipe, a gas transition device, a flowing separating block and an auxiliary block. A powder gas mixing through hole is formed in the flowing separating block. The gas supply mechanism comprises a plurality of oxygen guiding and conveying pipes and a plurality of second communicating pipes. The flame holder comprises a flame holder frame, an ignition device, a plurality of flow storage pipes and a plurality of diversion pipes. Using is convenient, and the plastic spraying effect is improved effectively.