Multivariate volatility modeling is always a hot topic in academic research. It is difficult to consider how to construct multivariate joint distribution. Copulas, a statistic method, can be used to decompose multivariate joint distribution into marginal distribution and correlation structure. This advantage is applied into calculating the dynamic VAR of a portfolio in the paper. Furthermore, a new model for dynamic portfolio choice based on copulas is proposed, and empirical analysis is operated for the several typical discrete manufacturing processes in the end.