The Postal Transportation Problem(PTP)is a very complex transportation problem. It has not any very effective solving method at present. This paper systemically analyze and define the problem according to its range, capability and time limit restrictions, random factors, dynamic factors, preferential factors, optimization objectives, cost composing, and so on. The multiobjective optimization mathematical modelof PTP is established and its relational problems are also analyzed. And the model is made up of 12 kinds of restraint conditions and three optimization objectives which are the whole transportation cost, average transportation time of mail and average use ratio of cars. This will be in favor of further study of PTP. The successful development of a logistics scheduling and dispatching optimization software based on the model and its corresponding algorithm proves the correctness of the model.[WT5HZ]