Aiming at a desirable solution to the high cost of precision navigation and positioning in the ocean, transmitting real-time service data from multi-global navigation satellite system through BeiDou short-messages device to realize real-time precise point positioning was proposed. Real-time service data was simplified to reduce the costs of communication and hardware, remedying the shortage of BeiDou short-message band width. In order to overcome the low communication frequency limitation of BeiDou short-message service, and to obtain satellite orbit position and clock correction at the time beyond minute interval, a method of forecasting real-time precise ephemeris was adopted. The data process of real-time precise point positioning in ocean based on BeiDou short-message was simulated. Post-processing ocean observation data and testing positioning performance, its accuracy can reach cm-level in horizontal direction and 10～20 cm in vertical direction. Results show that the method can provide effective technical reference for the low-cost real-time precise point positioning in the ocean.