Thermogravimetric analyzer has been employed in this paper to test the combustion properties of four kinds of mixed biomass fuel with sludge, domestic waste, swill, coal and grass as major components. Combustion characteristic parameters were obtained through series of experiments, and burning activation energy was got by kinetic analysis. Research results show that ignition temperature of mixed biomass fuel was relatively low and the mixed biomass fuel could be burned easily. The calculated burnout characteristics index and combustion characteristic index showed that combustibility of sample A is the worst while sample D is the best among four materials. Combustion kinetics calculations about the four samples showed that average activation energies for A, B, C and D under the low and the high combustion temperature are 47.02 kJ/mol and 50.51 kJ/mol, 28.10 kJ/mol and 26.98 kJ/mol, 27.93 kJ/mol and 26.72 kJ/mol, and 23.26 kJ/mol and10.73 kJ/mol, respectively, which present the order of activity: D>C>B>A. Results indicated that sample D has the best component proportion which could easily break down and burn out. Furthermore, combustion characteristic index of mixed biomass depends on the proportion of components, where the lower proportion of domestic waste in mixture, the better combustion characteristic index of mixed biomass fuel.