Abstract: The pyrolysis of Shenfu (SF) coal, algae and their blends (with 5%, 10%, 20%, 40%, 80% of algae in dry mass) was investigated by thermogravimetric analysis. The results indicate that the extremum temperature of devolatilisation of algae is lower , and the pyrolysis rate is faster than that of SF coal. Due to the complex composition, high content of volatiles and instable bonds, the algae is destroyed easily at low temperature and has a high devolatilisation rate. After the devolatilisation of algae at low temperature, the exposed ash covers the surface of the coal when algae co pyrolysises with Shenfu coal. The alkali and alkaline earth metals in algae ash have catalytic effects, and can accelerate the pyrolysis reaction, bringing forward the devolatilisation of coal. When the mixing ratios of algae are 40% and 80%, the synergy effect is significant, and the char yield is lower than the theoretical value.