A communication system, gateway, terminal, and communication method based on LoRa technology are provided. The system includes: a gateway configured to transmit an LoRa data packet containing a preamble, wherein duration of the transmission of the preamble is n1; and a terminal configured to perform channel activity detection one time for a duration of q1 each time after sleeping for a duration of p1, continue to sleep for the duration of p1 in response to the preamble not being detected, or receive and process the data packet and then continue to sleep for the duration of p1 in response to the preamble being detected, wherein p1>q1, and p1+q1 is less than or equal to n1.