Abstract: Lithium bromide absorption heat pump is used in the heating system of a subcritical thermal power plant. During the heating period, lithium bromide in the heat pump leaks into the heating and drainage system of the heating network and the water vapor circulation system of the unit. The online chemical instruments of the unit monitors the abnormal water vapor quality of the unit, and the boiler water wall tube burst accident occurs, and the unit stops urgently. After the shutdown of the unit, the water wall was sampled and analyzed, and the water quality test results of the thermal system were analyzed. It was determined that the water wall tube burst was caused by lithium bromide entering the thermal system. The results showed that after lithium bromide entered the water vapor system, the pH of the feed water decreased, and the minimum decreased to 6.81. The electrochemical reaction of lithium bromide at high temperature caused the microstructure of metal matrix to change, and a large number of intergranular cracks led to the decrease of metal strength. Under the action of high temperature and high pressure, the water wall tube bursted.