Abstarct: An innovative design concept that can be used for retrofitting existing bridges as well as for designing new bridges involves the utilization of prestressing in composite steel-concrete bridges. Prestressing the steel in a composite steel-concrete beam increases the load at which the steel beam yields, and also increases the ultimate strength of the composite section. At the same time, precompressing the tension flange improves the fatigue strength. We have tried to study the performance of prestressed composite beams under positive moment using ABAQUS software. First, a numerical model was simulated from a beam which had prestressing bars along the bottom (tension) flange and was subjected to positive bending moment (Hamid Saadatmanesh et al experiment, 1986). The accuracy of this modeling was approved because there was a good agreement between the results of the numerical method and the results of the experimental sample. Using finite element analysis, we studied the effects of parameters such as tendon eccentricity, larger tendon area and higher prestressing force on the behaviors of prestressed composite beams, afterwards. Analyzing the results showed, prestressing a conventional composite beam can significantly increase the load at which first yielding occurs and the ultimate capacity of the beam.