1. A Licensed Assisted Access (LAA)-based wireless transmission access method, applied to a baseband unit (BBU), comprising: acquiring a signal format corresponding to a Listen Before Talk (LBT) startup indication, the signal format comprising: a first signal format corresponding to a same manufacturer which is identical to a manufacturer for the BBU; a second signal format corresponding to a different manufacturer which is different from the manufacturer of the BBU; or a first signal format corresponding to a same manufacturer and a second signal format corresponding to a different manufacturer, delivering an LBT startup indication message, the startup indication message comprising the signal format corresponding to the LBT startup indication, receiving idle/busy state information of an unlicensed spectrum in response to the startup indication message; determining a preemptable unlicensed spectrum corresponding to the signal format according to the idle/busy state information, and delivering an occupancy message, the occupancy message comprising information of the preemptable unlicensed spectrum and a signal format corresponding to the preemptable unlicensed spectrum, receiving a release message of the preemptable unlicensed spectrum, the release message comprising the signal format corresponding to the preemptable unlicensed spectrum at the end of occupancy; and acquiring the signal format in the release message, and delivering the LBT startup indication message of the acquired signal format.