Abstract: In this paper, making the seventy-five countries as simples, we first use computing methods of Passche weighted and simple average to present an index design method of change rate based on formation principle of index, and then work out stock price indexes of Asia-Pacific, America and Europe, respectively.We draw up a unified index of global stock market according to the three regions.Finally, we empirically make a analysis of the correlation.between world stock index and region stock index.We use Granger causality method to test the causal relationship between world stock index and GDP.The results indicate that world stock market is the "barometer" of world' national economy.