The invention relates to an MIMO-based (multiple input multiple output-based) topology-transparent broadcast transmission multiple access method in an ad hoc network. By modifying the time slot structure and signal flow on the basis of MIMO-TTR (multiple input multiple output-topology-transparent reservation) protocol, the broadcast transmission can be effectively supported by the MIMO-TTR protocol in the topology-transparent network. The MIMO-based topology-transparent broadcast transmission multiple access method comprises the following steps: firstly, carrying out the time slot allocation on all the nodes in the network by the GRAND (Galois radio network design) algorithm in advance, wherein, each time slot is divided into the following stages: RTS (Request to Send), NTS (Not to Send), DATA (Data Transmission) and NAK (Non-acknowledge), and the broadcast transmission services are provided by using different MIMO data stream numbers in the four stages of the time slot; and exchanging the RTS / NTS subgroups by only one data stream at each transmitting node and each receiving node in the exchanging process, if the broadcast services are required to be transmitted by the transmitting node, the RTS subgroup is transmitted to all adjacent nodes for reservation in the allocated time slot, and if the RTS subgroup is not properly received by the receiving node, the NTS subgroup is replied to the transmitting node immediately, if the NTS subgroup is received by the transmitting subgroup, that the broadcast services cannot be transmitted in the current time slot is determined, and the next allocated time slot reservation is made, and if not, that the reservation is made is determined by the transmitting node, and the broadcast subgroup is transmitted by using all the data streams.