Describing the dynamic correlation of wind/solar power output and the fluctuation of joint output accurately are of great significance to the output forecasting and economic dispatch of the wind solar hybrid system. According to the problem that the existing static correlation coefficient cannot accurately describe the relationship between the wind power and PV output, this paper studies dynamic correlation of wind/solar power output and proposes a wind/solar power joint output model construction method by using dynamic Copula function. Combining with the measured data, it establishes 8 groups of wind/solar power joint output model, applies dynamic correlation coefficient to describe dynamic correlation of wind/solar power output and uses goodness of fit method to prove the superiority of the dynamic Copula model comparing to the static model to select the optimal model. Finally, the model is applied to the data driven wind/solar joint system, and the rationality and correctness of the model are verified. This work is supported by National Key Research and Development Program of China (No. 2017YFB0902600), Science and Technology Project of State Grid Corporation of China (No. SGJS0000DKJS1700840), and National Basic Research Program of China (973 Program) ( No. 2015CB251301).