The utility model discloses a safety and stability type auxiliary agent filling device, including gate valve, auxiliary agent metering tank, auxiliary agent pump and measuring pump. The nitrogen gas pipeline is connected with first gate valve one end and fourth gate valve one end, the auxiliary agent metering tank is connected to the fourth gate valve other end, the one end of second and the 5th gate valve is connected to the first gate valve other end, the second gate valve other end is connected the auxiliary agent and is pumped the end, barreled auxiliary agent pipeline is connected through three gate valves to auxiliary agent pump incoming end, auxiliary agent metering tank incoming end is connected to the 5th gate valve other end, the one end of the 7th and the 9th gate valve is connected to auxiliary agent metering tank output through the 6th gate valve, first measuring pump incoming end is connected to the 7th gate valve other end, second measuring pump incoming end is connected to the 9th gate valve other end, first measuring pump and second measuring pump output pass through the gate valve and connect styrene reaction system pipeline. The utility model relates to a rationally, simple structure, easy preparation, through twice measurement, can use quantity to carry out precise measurement to the auxiliary agent, ensured the normal clear of production, improved the productivity effect.