Ups and downs control was one of the main contents in control of the submersible. A new ups and downs control system was used on the submersible with piston type. Its mechanism structure and experiment platform was introduced firstly in this paper. Then the theory design, underwater experiment and finite element analysis of piston cavity was made separately to verify its design reliability and stability. The results of experiment and emulation suggest that the piston type submersible design was reasonable, feasible and practical.