The invention relates to a pilot diaphragm type reducing valve which comprises a valve body. An outlet channel and an inlet channel are formed in the valve body and are formed oppositely. A division body is arranged between the inlet channel and the outlet channel. A diaphragm is arranged above the division body and is of an arc downward-concaved structure. The lower surface of the diaphragm is connected to the division body in an abutting manner to close the inlet channel and the outlet channel. A cover plate is arranged above the diaphragm. The edge of the cover plate is fixed to the valve body. The edge of the diaphragm is clamped between the cover plate and the valve body. A control cavity is formed between the cover plate and the diaphragm. A pilot valve is arranged on the outer portion of the valve body, an inlet of the pilot valve communicates with the control cavity, and an outlet of the pilot valve communicates with the outlet channel. The outer side of the valve body is connected with a connecting pipe, one end of the connecting pipe communicates with the control cavity, and the other end of the connecting pipe communicates with the inlet channel. The pilot diaphragm typereducing valve has the effects of being small in number of components and simple in structure.