The long-span prestressed tension-string pipe beam is a new type of structure for transportation pipelines crossing rivers or trenches, with a span of up to 100. 150m. Taking a 100m span prestressed tensioned string pipe beam as prototype, a 1:15 scale model is designed, and the whole process of stress testing of the tensioned string pipe beam in the prestressed tension stage, the normal use stage and the ultimate bearing capacity stage is carried out for the first time in China. The nonlinear finite element simulation of the whole test process is carried out based on ANSYS, and combined with the uniform defect mode method and the cylindrical arc length method, the buckling analysis considering both the initial geometric defects and geometric nonlinearity is carried out. The experimental study and finite element analysis show that the half-span load is unfavorable to the prestressed tension-string pipe beam, and the overall deformation and upper string stress of the structure increase rapidly. The structure is more sensitive to out-of-plane geometric defects, and the critical buckling load under half-span load is slightly lower than that under full span load. The structure has reliable stability and large safety reserve, and the ultimate bearing capacity is 2.68 times of the design load. The calculated results of the finite element method agree well with the experimental results, which shows that the nonlinear finite element method used in this paper can simulate the whole process of the stress of the prestressed tension-string pipe beam. Finally, based on Rayleigh-Ritz method, the calculation formulas of deformation and internal force of prestressed tension-string pipe beam under elastic and elastoplastic conditions are derived.