Compared with the laboratory acoustic measurement of sediment samples, the in-situ acoustic measurement in marine sediment is considered more accurate and reliable, because it covers all of the surrounding environment factors and avoids the disturbance during the course of sampling and transporting of sediment samples. A new multi-frequency in-situ geo-acoustic measurement system (MFISGAMS) has been developed. The system can provide acoustic velocity (compression-al wave) and attenuation profiles of the uppermost 4～8 m sediment in the seafloor. It consists of 8 channels with 12 frequencies (multi-frequencies) and 0.5～2 MHz sampling rates. The data collected can be transmiuted in real-time. Associated with inclinometer and ,altimeter, it can provide the data for depth emendation. Acoustic velocity and attenuation data have been obtained from two in-situ experiments conducted in the Hangzhou Bay.