The price risk of Brent, Dubai and Minas Crude Oil market with GARCH model at Normal distribution is analyzed in this paper, and the results are examined by using Kupiec test. The price volatility is significantly described; price risks are measured as well. Because China sets its refined oil price according to Brent, Dubai and Minas Crude oil market, the correlation between the three markets are analyzed based on their historical data. The results present that the weights over the three markets at 0.2389: 0.5759: 0.1852 would be minimized oil cost volatility in China's refined oil market. The results are tested by Monte Carlo simulation，too. Giving the international oil price at 75 dollars/barrel and taking 95% confidence level, China’s oil cost volatility could be reduced 0.16-0.17 dollars/barrel in the method mentioned in this paper compared with common empirical methods.