The embodiment of the invention discloses a 3D printing auxiliary method and device and 3D printing equipment. The method comprises the steps that motion tendency information of a printed object, floating in supporting liquid in the printing process, in the vertical direction is obtained; the density of the supporting liquid is adjusted according to the motion tendency information, and therefore the motion tendency, corresponding to the motion tendency information, of the printed object is eliminated. According to the technical scheme, elimination of the motion tendency, in the vertical direction, of the printed object which is completely supported by the liquid in the printing process is counteracted by adjusting the density of the supporting liquid, the position of the printed object in the printing process remains stationary to the greatest extent through the supporting liquid, and the finished product quality is ensured.