The invention discloses a device and a method for testing soil structure characteristics under action of dynamic change of underground pressure water head. The testing system comprises a calibration tank, a loading device, a confined water control system and a measurement system and also comprises a corresponding data analysis method, wherein a cohesive soil layer and a sandy soil layer are arranged in the calibration tank in a layered mode so as to simulate to form an underground water-bearing structure; the confined water control system is formed by connecting a water tank which can be freely controlled to lift and a water inlet and outlet pipe; the measurement system comprises an electrical resistivity testing module, a soil deformation testing module, a water head pressure measuring tube, a micro pore pressure gage and a micro static penetrometer, and the electrical resistivity testing module consists of testing electrodes in the circular and vertical directions. The calibration tank serves as a bearing device and is matched with other several systems, so that the change of soil structure characteristics under complex conditions of dynamic change of the underground pressure water head can be dynamically tested, the influence on the soil characteristics is further analyzed, and basic data is provided for evaluating the structural behavior and health state of underground construction under complex conditions.