Based on econometric vector auto2regression model , this paper mainly investigated the long2run and short- run as well as causal relationships of international trade between China and Japan. We apply the Wald test ap2 proach of one-way effect causal measures presented by Yao and Hosoya (2000) to analyzing seven selected macroe2 conomic data of China and Japan over the span of the recent twenty years. We showed how the Wald test is put into the analysis of macroeconomic activities and how to interpret empirical evidence in view of the causal measures. Based on the observed one-way effect causal measures in cointegrated vector time series , the characterizations of causal structure among the selected economic indices are revealed. It was showed that Japanese interest rates in gen2 eral cause the other variables but not the other way around. The external trade causes monetary economy but not in the other direction. Even so , the monetary economy causes the imports from China. As for the effects of external trades to Japanese economic growth , the cause is mainly from exports but it is not long- run. The imports from China do not affect Japanese economic growth. The empirical results support the common understanding that the economic development of Japan and that of China are cooperative in the period we dealt with , at least in the meaning of inter2 national trade. We can see the Wald test of one-way effect causal measure provides an efficient approach to analyz2 ing complex economic system