The present invention is applicable to the field of communications and provides a transmission method, a system, and a communication device for realizing coexistence of data and voice services. The method includes: acquiring an idle timeslot available when voice transmission is performed by using DECT; and performing Wi-Fi transmission in the idle timeslot available when voice transmission is performed by using DECT. In the present invention, an idle timeslot available when voice transmission is performed by using DECT is first acquired, and then the idle timeslot available when voice transmission is performed by using DECT is used to perform Wi-Fi transmission, so as to realize coexistence of Wi-Fi and DECT in a time division multiplexing manner. In this way, a mutual interference problem when Wi-Fi and DECT coexist can be solved, a communication capacity of an entire communication system can be significantly improved, and moreover, there is no need to add a high-performance filter, thereby reducing costs for coexistence of Wi-Fi and DECT.