Conventional optimal active power dispatch research generally does not consider the influence of small-signal stability. When the operation condition is stressed， the optimal results， although is economical， might not meet the small-signal security requirement. The optimal active power dispatch with small-signal stability constraints is investigated. Based on the conventional active power dispatch model， an optimal active power dispatch model constrained by small-signal stability is built in order to ensure that the optimization result meets the given small-signal stability criterion. The successive linear programming（SLP）method is suggested to solve the problem. The proposed method is validated on a 4-generator test system and the New England 39-bus system.