A tow-pontoon with simple structure,reliable performance and low cost has been designed to help suspend equipments and meet the urgency according to the weight and dimension of the large underwater equipments and the dimension of the experiment pool and its in-line pool.The tow-pontoon is full welded body consisting of the steel structure bearing frame and steel plate flotage crust and I-shaped suspend girder.The strength and stiffness of the pontoon and I-shaped girder was verified by COSMOS finite element software.The experiment of lifting large underwater equipment was successfully done,at the same time the weight of underwater equipment was calculated.