A large adiabatic detonation calorimeter has been designed to determine detonation heat of explosives.The maximuaii tested sample is 50g with shell,which can be detonated in vacuum or in nitrogen atmosphere, The detonation heat (△H_det) of more than 20 high explosives was determined.The results indicated that for composite explosives,there was a linear accumulative relationship between heat of detonation and its composition,and the former could be calculated from the latter.