The invention discloses a method for measuring the dynamic deflection of a bridge. The method includes steps of determining deflection measured points according to the structural type of the bridge, and mounting pressure transmitters and acceleration sensors at the various measured points; collecting data of pressures of liquid in a communicating tube at the various measured points and acceleration data of the various measured points; enabling a data processing unit to receive the data and process the acquired data according to a first data model to obtain the dynamic deflection of the various measured points. The method for measuring the dynamic deflection of the bridge has the advantage of high bridge dynamic deflection measurement accuracy.