The invention is a shortwave-based weather data transmitting method and system, composed of master control computer, network controller, shortwave station, transmitting aerial, receiving antenna and shortwave receiver, where RS-232 terminal of the network controller is connected with COM1 or COM2 port of the master control computer, ACC1 terminal of the network controller is connected with REM1 terminal of the shortwave station and the shortwave receiver is a shortwave single-sideband receiver. Classify the real-time collected weather information by the master control computer to generate weather forecast information data of each sea region, primarily input the information data to the network controller for grouping, convert the grouped information data to audio frequency information to send to the shortwave station, adopt shortwave single-sideband channel to transmit multiple packets in multicahnnel packet auto-transmitting mode, adopt a multichannel auto-scanning receiving mode to receive them many times, join and integrate the exact data according to packet number into a piece of complete information. It can provide accurate, in-time, reliable weather forecast information service and other business service for moving ships.