The invention discloses a membrane-protecting air source loop for a pneumatic diaphragm regulating valve executing mechanism. The membrane-protecting air source loop comprises at least one air supplying air channel. One ends of inlet ball valves inside the air supplying air channels are used for being connected with a pressure air source, and the other ends of the inlet ball valves inside the airsupplying air channels are connected with air inlet working openings of pneumatic control two-position two-way reversing valves and air inlet working openings of pneumatic control two-position three-way reversing valves. Air outlet working openings of the pneumatic control two-position two-way reversing valves are connected with inlets of first one-way valves and control openings of the pneumaticcontrol two-position three-way reversing valves, and outlets of the first one-way valves are connected with control openings of the pneumatic control two-position two-way reversing valves. Air outletworking openings of the pneumatic control two-position three-way reversing valves are connected with inlets of pressure reducing valves, outlets of the pressure reducing valves are connected with oneends of outlet ball valves, and the other ends of the outlet ball valves are used for being connected with the pneumatic diaphragm regulating valve executing mechanism. The air inlet ends of safety valves are connected with outlets of the pressure reducing valves, and outlets of the safety valves are connected with the control openings of the pneumatic control two-position two-way reversing valves. According to the membrane-protecting air source loop, a membrane can be protected against high air pressure damage, and overhauling is convenient.