A digital 
overlay covering method includes a 
down link trunking and an up link 
trunking, wherein the 
down link trunking includes: receiving the signals, 
processing the signals, packing the framing digital signals, transmitting to a plurality of covering units through the 
optical fiber or five line transmissions, decoding the frame, completing the 
signal coverage transmitted by the antenna; the up link trunking comprises: receiving the 
signal, 
processing the 
signal, packing the framing 
digital signal, transmitting to the access unit through the 
optical fiber or five line transmissions, decoding the frame, transmitting to the 
base station system through the antenna of the access unit or the potical 
fiber / five line transmissions. The invention also provides a digital 
covering system. The method and the 
system of the invention adopt the 
digital signal processing, the 
digital signal transmission, the digital distribution, reduce the loss and the 
noise of the signal. An access unit is added at the entrance of the building, transmitted to the inside of the building through the wiring, and the coverage unit is accessed at the required position, namely reaching the requirement to be compatible of the multi-
system and multi-frequency range, to complete the coverage of the signal.