In the context of global integration, one country’s economic fluctuations will affect another country through a variety of ways, the global economic crisis in 2008 is the best proof. The economic ties between China and Japan are closely related. Japan was once the largest trading partner of China. It is very important to study the influence mechanism of economic fluctuations between China and Japan for the stable development of China’s economy. This paper selects China’s export to Japan(CEX) Japan’s export to China(JEX) Japan’s direct investment to China (FDI) Chinese gross domestic product (CGDP), Japan’s gross domestic product (JGDP) five variables. We use impulse response and variance decomposition to analyze the interaction of Chinese and Japanese economy. Finally we come to the conclusion: China’s economy affected by the impact of Japan’s economic fluctuations bigger than Japan’s economy affected by China; the contribution rate of imports from Japan is greater than the export to China’s economy.