The invention discloses a reaction kettle for polymerized ferric sulfate production. The structure of the reaction kettle comprises a kettle body, support feet, an upper sealing head, a pressure monitoring device, a connection protection rod and a motor, wherein the support feet are welded and connected on the outer surface of the bottom portion of the kettle body, the upper sealing head and the kettle body present an integrated molding structure, the upper sealing head is connected above the kettle body, the bottom portion of the pressure monitoring device is embedded and connected at the internal-upper portion of the upper sealing head, the pressure monitoring device and the upper sealing head form interference fit connection, the connection protection rod is vertically welded at the top end of the upper sealing head, the pressure monitoring device is arranged on the outer side of the connection protection rod through the upper sealing head, the motor is connected at the top end of the connection protection rod, the kettle body is provided with a support seat, an inner coil pipe and a base, the support seat is welded and connected at the outer surface of the kettle body, and the inner coil pipe is inserted into the interior of the kettle body in a connected manner. According to the present invention, the reaction kettle can accurately, effectively and real-timely monitor the air pressure condition in the reaction kettle, can grasp the dynamic air pressure in the reaction kettle, can avoid the damage caused by the too high air pressure difference, and can easily achieve the protection on the reaction kettle.