A J-lay crane barge named Double-8000, the two cranes of which have the lifting capacity of up to 8000t, is about to be constructed by Offshore Oil Engineering Co., Ltd. (COOEC) in order to meet the requirements of oil and gas development in South China Sea. This paper presents the overall structure design of the J-lay system and corresponding method for strength calculation. The hardware and software for the J-lay control system are also developed. The model test on such a designed J-lay system along with its control system is investigated by applying the similarity theory and the hybrid model test method. A specially designed platform simulating the motion of the crane barge in 6 degree-of-freedom (6-DOF) in different sea conditions is used for the model testing in order to get the results of the influence of the crane motion on the performance of the J-lay system. The model tests verify the functionality and safety performance of the system. The results show that the test data are in good agreement with the numerical simulation. It can be seen that the J-lay system can meet the challenging requirements of Double-8000 for pipeline laying in waters deep to 3000m in South China Sea.