Based on HP filter, China’s quarterly data between 1997 and 2011 are analyzed, the results show that the estimated deviation of real-time output gap and inflation gap can produce systematic impact on monetary policies and trigger excessive response to the policies and that this systematic influence is more significant before and after international financial crisis, therefore, central bank should reduce response coefficients of real-time output gap and inflation gap in policy rules, i.e. the real-time response coefficients of current monetary policies should be smaller than those theoretically estimated by calculation model. China should be more careful in making monetary policies, on the one hand, daily supervising work on macro-economic activities should be consolidated, on the other hand, a series of monetary policy instruments should be sufficiently used to make “micro-adjustment”, meanwhile, “firewall”for preventing outside impact should be studiously constructed.