Abstract: A green and flexible power system integrating distributed renewable energies（RE）, battery energy storage（BES）, voltage source converter based direct current（VSC-DC） transmission, et al facilitates the green-oriented transition of transportation. Considering the expansibility of transportation load and the variability of RE generations,an optimal capacity allocation algorithm is proposed for the source-network-load-storage integrated highway power system based on full-life-cycle chronological operation simulation and marginal utility analysis. Case studies on a typical highway service area verify that the proposed method outperforms in both planning accuracy and economical optimality. The optimal match between the dynamically growing traffic load and the stochastic RE generations is achieved and an improved net investment income is obtained.