Under the conditions of constant mixture equivalence ratio, in this paper an equilibrium constant method is adopted in calculating and contrasting equilibrium temperature, equilibrium pressure and detonation wave velocity of hydrocarbon - air system detonation combustion products, and based on this a further study of the law of mixture's influence on the features of detonation wave's parameters is made. The result shows that, under a constant equivalent ratio, both the equilibrium temperature and the velocity of detonation wave all increase with the increase of mixture's initial pressure, and gradually tend to a certain maximum. The relationship between equilibrium pressure and initial pressure seems to be a liner increase. Meanwhile, for the different fuels, the more the molecule weight is, the higher the equilibrium temperature is, and the greater the equilibrium pressure is.