Abstract：As a major economy that implemented unconventional monetary policy earlier, Japan has attempted the most radical monetary policy in the long recession. So studying the effectiveness of its monetary policy is of great significance to the global monetary policy adjustment strategy in the post-pandemic period. This paper analyzes the impact of Japanese monetary policy on macroeconomy under different levels of monetary policy uncertainty based on SE-IVAR model with monthly data from 1987 to 2021. The empirical analysis shows that:(1) Japan's monetary policy uncertainty has a significant effect on the effectiveness of Japan's monetary policy in short term, and the increase of monetary policy uncertainty will weaken the effect of monetary policy.(2) When the monetary policy uncertainty is high, the stimulus to output, core inflation, consumption and long-term interest rates decreases in the short term, and has a inhibitory effect on economic growth in the long term.(3) The unconventional monetary policy implemented after 2001 has a better effect on output than the conventional monetary policy, and the unconventional monetary policy is more affected by the monetary policy uncertainty than the conventional monetary policy.(4) Fighting against the deflation through conventional and unconventional monetary policy works only in the short term, and it is difficult to achieve moderate growth of core inflation in the long run.

Keyword：Japan's monetary policy; monetary policy uncertainty; effectiveness of monetary policy; SE-IVAR model; unconventional monetary policy;