To study the command and control system in an island air defence system under the background of systemic conflict, this paper proposes a new modelling method based on the opinion dynamics leader-follower model to simulate the target threat assessment process in the command and control activities. Through example simulation, it is obtained that in a centralised command and control system, a command post (CP)-led model can provide the most accurate threat assessment results, but it consumes a longer time. While in a distributed command and control system, a model without a leader can provide a target threat value accurately and quickly. The consistency of simulation results and actual situation indicates that, at present, under a high degree of battlefield information sharing, it is necessary to down-pass the authority of the CP to improve operational efficiency. In summary, the proposed model can comprehensively reflect the process that the island air defence system assesses the threat of an attacking target, and it gives a new idea for investigating the command and control procedure and system of the island air defence system.