The invention provides a hydraulic drive injection based bottom sediment acoustic characteristic in-situ detecting system, comprising a framework, a transceiving transducer and a transducer injection device. The system is characterized in that the injection device is a hydraulic injection driving device of a pulley combined mechanism, and comprises a hydraulic rod driven by a hydraulic pump, upper and lower movable pulleys fixed on the upper end of the hydraulic rod, three upper fixed pulleys fixed on the upper part of the framework and three lower fixed pulleys fixed on the lower part of the framework, wherein two steel cables pass through two through holes in the middle of a movable pressure plate, and are fixed on the framework by upward moving around the two upper fixed pulleys, the upper movable pulley and the other upper fixed pulley in turn, and are fixed on the frame by downward moving around the two lower fixed pulleys, the lower movable block and the other lower fixed block. The system is suitable for various types of bottom sediment substrates with remarkable injection effect and wide application range, has small interference to bottom sediment and small impact on the transducer with high stability and high detection accuracy, does not require real-time manipulation when full automatically working in sea bottom to reduce marine survey cost.