ABSTRACT: A new multi-parameter chemical sensor method to study the active hydrothermal mound of the seafloor as well as non-active massive sulfide mound was proposed. And this method has been used for investigation and study during the first two legs of the 26th COMRA cruise on the Carlsberg Ridge of the Northwest Indian Ocean and the TAG hydrothermal area. During 1st Leg, we found one hydrothermal field located at 3.5~3.8°N on the Carlsberg Ridge in which few investigation has been carried out for hydrothermal activities. The known TAG area was also investigated for comparing and evidencing the ready instruments, which is helpful to find a new method to survey the massive sulfide mound, and the chemical sensor method can provide the similar result as the Transient ElectroMagnetic and Electric Self-potential methods do.