In this article, a strategy has been made to allocate slot resource in coordinated airport in an efficient way. The strategy take the minimum cost of the air line net as the objective, restricted by the airport capacity and transportation requirement, and accord with the proportion of aircraft type on each air line. To simplify the decision of the proportion of the aircrafts, the air lines have been classified. The costs of each aircraft on different air lines are calculated by an engineering cost function. As the result shown, the strategy is close to the reality, and has a well expansibility.