Financial crises, like Asian financial crisis in 1997 and credit crunch from USA in 2007, have huge influence worldwide. For the importance and uniqueness of China's stock market, it is interesting and attractive to research it under influence of financial crises. The purpose for this research is to find out the influence of financial crises on Chinese stock market and focus on efficiency frontier. For research methodology, the efficiency frontiers are built using cross-sectional data through linear programming with an optimization model for different periods for Chinese stock markets portfolios and for a portfolio from Chinese, UK and USA stock markets together under current financial crisis. This research finds out that Chinese stock markets have a positive risk return trade off and it varies under the influence of financial crises; the investment efficiency in Chinese stock markets are relative good currently and if further diversified with western markets, higher investment efficiency can be achieved. The implication for this paper is to offer a suitable method to construct Chinese stock market efficiency frontier, and to improve investment efficiency through further diversification. This paper enjoys the originality that it perhaps is the first paper to build Chinese stock market efficiency frontier through linear programming.