Based on engineering practice, this paper proposed a new type of dam, longitudinal reinforced rockfill dam, which is built by a rigid structure(longitudinal reinforced body)with the functions of anti-seepage and bearing stress in the interior of conventional earth and rock dam. This rigid and flexible dam structure improves the operational safety of conventional earth and rock dam. In the analysis of deformation, it is theoretically deduced to consider it as a vertical fixed-end beam that bears the load of upstream and downstream water pressures as well as the force of rock-fill dam, especially the tensile load on the surface of the longitudinal reinforcement caused by the rock-fill settlement. At the same time, the longitudinal reinforcement split the continuous stress and strain of the dam shell material in the upstream and downstream of dam body, and the mechanical performance under various working conditions is closer to the behavior of retaining wall. According to the proposed designing and calculation method of the longitudinal reinforced earth and rockfill dam as well as the engineering practice, this paper mainly introduced the application of the proposed new type of dam in the design of the Fangtianba Reservoir in Tongjiang, Sichuan Province.