The hydration heat release rate and total hydration heat of copper slag powder cement composite cementitious systems containing different copper slag grinding time of 30min and 60min, and different admixture content of 0%, 20%, 30%, and 40% respectively were determined by isothermal calorimetry test to investigate the different levels of ground granulated copper slag powder and its content on the influence of hydration reaction mechanism of composite cementitious system, and calculate the hydration kinetics parameters based on Kstulovic Dabic model. The results show that copper slag powder delays the end time of induction period, the beginning time of acceleration period and the appearance of the second heat release peak, and reduces the heat release and hydration rate of composite cementitious system. Before hydration for 12h, copper slag powder inhibites and slows down the hydration heat of the composite cementitious system. After hydration for 12h, the activity of copper slag powder is gradually activated and the hydration rate is accelerated. The hydration reaction of the copper slag powder cement composite cementitious system undergoes the process of nucleation and crystal growth interactions at phase boundaries diffusion(NG I D). The hydration reaction rate curve of the copper slag powder cement composite cementitious system calculated by the hydration kinetics model of Kstulovic Dabic can well simulate the hydration rate curve obtained from the calorimetry test in sections. The crystallization and nucleation and crystal growth process(NG) of the composite cementitious system are prolonged with the increase of the content of copper slag powder and the decrease of the fineness, while the phase boundary changing reaction process(I) is shortened with the increase of the content of copper slag powder.