Transmission network planning and distribution network planning are all classical problems in power system. The coordination programing of these networks will lead to global optimal planning solution with the premise of a prescribed investment budget. In order to tackle the issue of combinatorial explosion in the coordinated planning, a bi-level calculation method based on the project-net revenue curve of distribution network is proposed. By solving the distribution network planning model repeatedly, project-net revenue curve is obtained and passed to the transmission network expansion model. This method significantly reduces the number of integer variables in the coordinated planning problem. In case studies, transmission & distribution testbed based on the modified Garver’s 6-bus system and the REDS-135 system verifies the effectiveness of the proposed method.