The invention discloses a control setter beside a diesel engine for stepless voltage regulation of air pressure. The control setter is used for the field of diesel engine manufacturing. The control setter comprises a shell, a sliding sleeve, a valve rod and a valve seat piston; a sliding sleeve sliding cavity and a valve seat piston sliding cavity are arranged in the shell, the sliding sleeve is arranged in the sliding sleeve sliding cavity, and the valve seat piston is arranged in the valve seat piston sliding cavity; the sliding sleeve forms a first air cavity in the sliding sleeve sliding cavity, and a second air cavity is formed in the valve seat piston sliding cavity between the sliding sleeve and the valve seat piston; a first air through hole is formed in the sliding sleeve, and a second air through hole is formed in the valve seat piston; a first valve body and a second valve body are arranged on the valve rod; a valve rod spring is arranged between the sliding sleeve and the valve rod, a sliding sleeve spring is arranged between the sliding sleeve and the valve seat piston, and a balance spring is arranged at the bottom part of the sliding sleeve spring; and an air inlet hole and an air outlet hole are formed in the shell. According to the control setter, during working, high-pressure air is hardly consumed, so that operation cost of the diesel engine is saved; stepless voltage regulation of the output air pressure and stepless speed change of the rotating speed of a crankshaft of the diesel engine are realized; and the control setter is compact in structure, safe,reliable and easy to maintain.