By maximizing the central bank utility, this paper uses maximum principles to build a dynamic optimization model of central bank utility, and discusses the effect of economic subject behavior on the monetary policy transmission validity. It turns out that, firstly, the length of time on monetary policy transmission is directly determined by the sensitivity of commercial banks to the monetary policy signals; secondly, under expansionary monetary policy, the response of commercial banks is more important than the response of enterprises and residents, while under tight monetary policy, the response of enterprises and residents is more important than the response of commercial banks. Optimizing the behaviors of commercial banks, enterprises and residents can effectively improve their sensitivity to the monetary policy signals, and therefore improve the monetary policy transmission validity.