The International Telecommunication Union (ITU) defines the uplink for ship-to-satellite communications for the VHF Data Exchange (VDE) subsystem of the VHF Data Exchange System (VDES). This paper studies a demodulation and decoding technology for VDE uplink signal to realize uplink physical layer communication. Firstly, the data-aided and non-data-aided methods are used to estimate and correct the frequency offset and phase offset, and the timing recovery algorithm is used to achieve symbol synchronization. Secondly, the ID segment and the data segment of signal are decoded by using the majority-logic decoding algorithm and the iterative decoding based on the Max-Log-Map algorithm respectively. Finally, the whole system is simulated. According to the results, under the frequency offset of 4 kHz, when Es/N0≥5 dB， the error probability of signal ID decoding is less than 0.01, and the frame error rate of data segment is less than 0.1, which shows the effectiveness of the algorithm under large frequency offset.