Research conclusions:The essential of the algorithm is to create the equilibrium equations related to primarymoments,and an iterative approach is adopted to solve the equations to calculate concrete stress and reinforcement stress in reinforced concrete slab. A computer program corresponding to this algorithm is developed. A lot of real calculation examples show that this algorithm can obtain the fastconvergence in iterative process and accurate resul.t This algorithm can also simulate some special actions of loaded slabs. If this algorithm is used in actual design, it can calculate the theoretic areas of main bar and additional bar needed when the structure subjected to all kinds of load cases,furthermore, the envelop curve of steel area is captured forpractical application.