This paper uses a grey forecasting model GM(1,1) on improving the investment performance of classical Markowitz efficiency frontier's investment portfolio using the component markets' indexes of MSCI World Index from 1999 to 2005 as the samples. Using grey Markowitz efficiency frontier's investment portfolio models, we establish a more stable and correct connection between ex-ante model and ex-post performance. The results show the Grey Markowitz efficiency frontier investment portfolio model could improve the investment performance effectively and stably.