Aiming at the problem of long-range air defense early warning of large surface warship formation, the deployment of air defense sentry ship is studied. Based on the in-depth analysis of the advantage of air defense sentry ships in long-range early warning, the deployment models of single and two air defense sentry ships are respectively established. And the detection capability, fire strike capability, the speed of shipborne air defense missile and the penetration target are taken into account. The superiority and feasibility of the model are demonstrated through simulation calculation, and the conclusion of optimal deployment of air defense sentry ship of large surface warship formation is obtained, which can provide references for deployment of air defense sentry ship formation.