Abstract: Aiming at the problem of secure transmission of information in multi-hop relay transmission system, this paper proposes a secure transmission scheme based on multi-node cooperative jamming (FD-MCJ) in full-duplex mode. The scheme uses the relay in the communication network to send jamming signals to worsen the receiving performance of the eavesdroppers, and the relays adaptively choose the secure transmission scheme in two cases, according to the channel state information. In this paper, the Poisson point process is used to model the position of eavesdroppers. Then, on the basis of the availability of CSI, different specific schemes of secure transmission are given. Considering the hop number of the system, self-interference between antennas, transmitting power and jamming power. the closed expression of the system secrecy outage probability under FD-MCJ scheme is derived. Finally, numerical analysis and Monte Carlo simulations show that the theoretical derivation is correct and the use of full-duplex multi-node cooperative jamming scheme in multi-hop relay system can effectively improve the security performance of the system. Key words: multi-hop relay system; physical layer security; cooperative jamming; channel state information; stochastic geometry; full-duplex; secrecy outage probability;