In order to realize the mechanization of kelp harvest and transfer and reduce the working intensity of kelp harvest, the existing kelp cultivation raft model was improved to connect the kelp seedling rope into strings from the beginning to the end in turn, so as to facilitate the mechanized harvest and transfer of kelp, and design and try to make rotary retractable claw type harvest and transfer experimental device. The unit numerical algorithm was used to calculate and analyze the tension and drag force of a string of kelp seedling rope during harvesting, and analyze the influence of different dragging angles of seedling rope on the running state of the transfer device. The calculation and analysis and bench test results show that the tension of kelp harvest and transfer device on the attached kelp seedling rope is 1 290 N. The retractable claw cannot lift the seedling rope and the rope will be taken off when the lifting angle of the kelp seedling rope is lower than 15°. The retractable claw can successively lift the kep seedling rope and the kelp can pass through the transfer device smoothly when the lifting angle of the kelp seedling rope is greater than 15°, so as to achieve the purpose of kelp harvest and transfer. The test run of rotary retractable claw type harvest and transfer device is good, and the sequential retractable mechanism can effectively solve the key problem of claw wound by kelp in the process of harvest and transfer. The hydraulic system is designed with superposition hydraulic control one-way valve, which can solve the problem of rapid drop of tubing leakage boom and improve the safety of the system. The test results show that the technology of rotary retractable claw type harvest and transfer is feasible and can lay a solid foundation for sea tests.