Synchronous behavior is a ubiquitous phenomenon in nature.Under certain conditions，a number of mechanical metronomes，which are given an arbitrary initial phase，will reach the synchronized state of motion after a period of time. In this paper，firstly，we establish the dynamic equation of a single metronome by analyzing its internal working mechanism.According to the experimental results，the laws of the change of the resistance moment and the dynamic moment with time are given.Then the coupling action between the metronome is represented by the inertial force，so the dynamic equation of the metronome system is established with much more clear physical meaning which can better explain the synchronization phenomenon of the metronomes with the same swinging period on the horizontal board.The theory can be used to predict the time of the metronome system to achieve the synchronization，meanwhile，this theory model shows the good universality under different experimental conditions.