In this article, the combustion characteristic of coal-ammonia composite is investigated. Raw coal and preheating modified coal are treated to absorb the ammonia. Four kinds of samples are made to conduct the thermal balance experiments. The results show that the content of ammonia in the coal-ammonia composite greatly affects its combustion characteristics. The coal-ammonia composite has a lower carbon emission than the raw coal when the same amount of heat is released. Besides, the performances of raw coal can also be improved by preheating treatment, but the coal-ammonia composite has better combustion performances with the same amount of calorific value.