The invention discloses an auxiliary device capable of changing the photoelectric conversion efficiency of a solar battery piece. The auxiliary device comprises a cylinder barrel with one end opened, and a cylinder cover connected with the opened end through a bolt. A first oil pipe and a second oil pipe are arranged on the side face of the cylinder barrel. A piston and a guide sleeve are arranged in the cylinder barrel. A piston rod is fixed through the piston. The end, facing the cylinder cover, of the piston rod movably penetrates the guide sleeve and the cylinder cover and is connected with an output head through a bolt. Annular piston gaskets are arranged at the two ends of the piston. The outer diameter of the annular piston gaskets is equal to the inner diameter of the cylinder barrel. The inner diameter of the annular piston gaskets is gradually increased along piston to the two ends of the cylinder barrel. The inner diameter of the first oil pipe and the inner diameter of the second oil pipe are gradually increased from the ends, located on the cylinder barrel, to the other ends. According to the auxiliary device, due to the fact that the annular piston gaskets are arranged, in the low-temperature environment, even the phenomena that the flowing speed of hydraulic oil is low and part of the hydraulic oil is solidified happen and consequently the acting force acting on the piston is small, the device can be allowed to work normally through a hydraulic oil pump under the condition that no excessive power consumption is added and higher output pressure is provided.