Thermagravimetric and combustion characteristics of binderless fiberboard (BF) were investigated. Fibers prepared by traditional heat grinding (FB) and which prepared in the presence of trivial inorganic acid during grinding (FBA) were used as compared. The results show that the total weight lost during thermal decomposition following as: BF > FBA > FB. The order of initial decomposition temperature was that FB > BF > FBA. Thermagravimetric weight loss rate in pyrolysis of woodfiber and binderless fiberboard got from adding minim inorganic acid in the heat grinding system to heat grinding were faster compared to the woodfiber made by heat grinding. Combustion characteristics results revealed that heat release rate and total heat release amount of BF were larger than that of FB. Smoking ratio of BF was larger than that of FB before the flaming combustion, but t less than that of FB after the flaming combustion. The concentration of produced CO2 and CO for BF during combustion was higher than FB.