This study take seven International Monetary Fund (IMF) reserve currency (COFER) currency and Renminbi as a foreign portfolio. We firsy apply Markowitz(1952)'s MV model to establish the optimal currency portfolio. In addition, we compare its performance with an equal weighted protfolio model. Secondly, We use the Variance-Covariance model and DCC-GARCH model to measure the portfolio Value at Risk, and finally using the back-testing to test the performace of the two models. The results show that, DCC-GARCH-VaR is better than the VAR-COV-VaR model, and through a portfolio approach with MV model construction can reduce the investor's risk diversification and achieve the purpose of the minimum risk.