Rational transmission pricing mechanism is a key issue for the development of cross-regional electricity trading. In this paper， network pricing method based on the summation of multiple networks and the whole network uniform pricing method are compared in details. Considering the characteristics of regional grid and assets structural， the whole network uniform pricing idea is introduced and the transmission pricing method integrating transmission cost allocation and transmission income assignment is proposed. Firstly， the nodal marginal cost and the regional network charge are calculated based on network running state; then the regional network charge is reassigned among network owners considering transmission line length and electricity trading. Case study using the IEEE 30-bus test system demonstrates the validity and novelty of this method. It also shows that the regional network charge can be calculated reasonably and the development of cross-regional electricity transaction is promoted effectively.