This paper proposes an ordering relation named Admissible Subgoal Ordering (ASO). The definition of ASO is formalized, and its relative importance for incremental planning is discussed. Then, this paper introduces the notion of dependency relations over facts, and develops fact dependency graph technique that can approximate admissible ordering relations in polynomial time. Finally, an algorithm to compute subgoals sequence with admissible orderings is presented. All the ideas presented in the paper are implemented in the planning system ASOP, and the effectiveness of the techniques is demonstrated on the benchmarks of International Planning Competitions (IPC). The results show that these techniques can efficiently solve large planning problems and lead to a greater improvement in planning performance.