The route planning of aircraft in sonobuoys deployment for searching submarine is studied. It is proposed that the sonobuoy array can be abstracted into a point set on the plane. Analysis is made to greedy algorithm, the commonly used route planning optimization method; and we find that when there is a point-set expansion, the greedy algorithm would diverge from the globally optimal solution. Then, in order to optimize the route, a more reasonable method named ant colony algorithm is used. Compared with greedy algorithm, ant colony algorithm could attain a better route. Simulation proves the effectiveness of the method.