The invention provides a communication method based on a Beidou system. The method comprises the following steps: step (a), converting a data source sensing value into a three-bit hexadecimal compression code under a variable scale; and step (b), carrying out data frame assembly by adopting a multi-mode mode. According to the method, data compression is realized by adopting a compression algorithm. In order to meet the difference requirement for data observation frequency in fishery observation, the data assembly algorithm based on the detection frequency is adopted for achieving assembly of data with different detection frequencies, and meanwhile by means of the optimized assembly algorithm under multi-mode fusion, the single-time data sending efficiency of short messages is improved under the condition that the detection frequency is met.