The invention discloses an oil filling device for a nuclear-grade capillary pressure transmitter, belongs to the technical field of nuclear power plant reactor pressure transmitters, and particularlyrelates to a pressure transmitter oil filling device for reliably and effectively completing oil filling work under complicated field conditions. The oil filling device includes a frame (1), a distribution box (2) and a magnetic stirrer (3). The distribution box (2) and the magnetic stirrer (3) are both disposed in the frame (1). The frame (1) includes a glass oil bottle (7), an oil storage tank (8), a vacuum flange (9) and oil filling hoses (12), wherein the glass oil bottle (7), the oil storage tank (8) and the vacuum flange (9) are connected in sequence to form a closed loop through the oilfilling hoses (12). The oil filling hose through which the glass oil bottle (7) and the vacuum flange (9) are directly connected is provided with two branch pipes, a vacuum gauge A (4) is connected to the branch pipe close to the glass oil bottle (7), and a vacuum pump (6) is arranged on the branch pipe close to the vacuum flange (9).