The invention relates to a circulation heating system for a steam heater. The system comprises a main liquid supply box, a circulation heating pump, the steam heater, a pneumatic cut-off valve, a temperature sensor and a stirring device, wherein the stirring device is arranged in the main liquid supply box; a pipeline between the main liquid supply box and the steam heater is provided with a flow sensor; the main liquid supply box is provided with a circulation heating liquid outlet F1 and a liquid return port F2; a saturated steam pipe is provided with a branch pipe with a second pneumatic cut-off valve; the first pneumatic cut-off valve, the second pneumatic cut-off valve, the circulation heating pump, and the flow sensor and the temperature sensor are under interlocking control of a programmable logic controller PLC; the installation position F3 of the temperature sensor is positioned below the lowest operating liquid level of the main liquid supply box; and the temperature sensor is immersed in a heated medium. The system has the advantages of improving the circulation heating efficiency of emulsion, enhancing the safety, treating the fouling, blockage and the like of the heater and the like, along with convenient operation; and the system can protect the circulation heating pump under the condition that the heater or the pipeline in the heating system is blocked.