As the main tools of macroeconomic management, fiscal policy and monetary policy need to implement different policies according to different components of economic fluctuations. Unlike developed countries, whose macro-economies are dominated by business cycle fluctuations, China's macro-economy is dominated by relatively low-frequency medium-term and long-term cycle fluctuations. Based on counterfactual analysis and spectral variance decomposition using historical data, this paper examines the heterogeneous effects of fiscal and monetary policies on different components of macroeconomic volatility. The result of research shows that in terms of output, both fiscal policy and monetary policy shocks contribute to the changes of the business cycle fluctuations. In addition, fiscal policy can also explain the components of higher frequency fluctuations, while monetary policy shocks also contribute to the changes of the more low-frequency medium-long cycle fluctuations. Regarding inflation, monetary policy shocks have a high contribution to different cyclical components, while the contribution of fiscal policy shocks is relatively weak. The research findings of this article highlight the importance of scientifically identifying different cyclical components in macroeconomic fluctuations and emphasize the need to consider the differences in cyclical components when discussing the coordination and cooperation between fiscal and monetary policies.