The invention discloses a temperature controlling method of a 3D printed part. The method comprises the steps that (1), a heat guiding ball is embedded in a printing chamber, and the height of the heat guiding ball is flushed with the height of a printing platform; (2), the annealing temperature of the heating device is set, and the heating device is controlled by the controlling system to heat the heat guiding ball; (3), the heating device is controlled by the controlling system to stop heating when the temperature of the heat guiding ball is the annealing temperature; (4), a printing systemis controlled by the controlling system to start a printing mode, printing consumed materials are extruded by the printing system on the printing platform to form the printed part, and a platform liftable system is lowered; (5), the heat guiding ball moves to the periphery of the printed part. The method has the advantages that the heat transmission to the printed part from the heat guiding ball and the pressure supporting on the printed part can be achieved to reduce the internally accumulated internal stress of the printed part, and therefore the subsequent ageing damaging speed of the printed part is slowed down.