The present invention discloses a message transmission method. A first portable device transmits an identity information of a first wireless signal transmitter and a message content to a cloud server. The cloud server analyzes the message content to obtain a message tag of the message content, and obtain a wireless signal transmitter tag of the first wireless signal transmitter according to the identity information. The cloud server then obtains at least one target identity information representing at least one target wireless signal transmitter by using the message tag and the wireless signal transmitter tag, to obtain an association between the message content and the at least one target identity information. When receiving a second identity information, a second portable device compares the second identity information with the at least one target identity information and receives the message content from the cloud server.