Abstract: In order to compensate the centroid variability of the underwater welding vehicle (named HITUWV) caused by the movements of the 3-DOF (degree of freedom) Cartesian-type manipulator, a centroid-variability model based adaptive sliding mode controller is proposed. Firstly, a centroid variability model (CVM) of HITUWV is established to describe the centroid variability characteristics of HITUWV accurately. Then, a centroid-variability model based adaptive sliding-mode controller (CVM-ASMC) is designed, to realize a high-accuracy compensation of the centroid variability. Experimental results indicate that the proposed CVM-ASMC demonstrates a higher accuracy, a better stability and a lower power consumption than the conventional PID (proportional-integral-differential) controller and the model-based PID controller. As a result, CVM-ASMC can meet the control requirement of underwater operation with high stability and accuracy.