Abstract: Precast prestressed box girders are widely used in bridge projects because of their advantages such as high bearing capacity and fast construction. The arrangement of prestressing strands, prestressing loss and concrete strength are the key issues in the design, construction and application of box girders. For this reason, this paper adopted the method of finite element analysis to study the effects of different prestressing strand arrangement, prestressing strength and concrete strength on the mechanical properties of assembled prestressed box girders. The results showed that as the number of prestressed steel strand rows increases, the initial stiffness and peak load of the box girder gradually increased, but the growth rate gradually slowed down. The closer the prestressing strand rows were to the bottom tensile side of the box girder, the more obvious the effect of bearing capacity enhancement on the specimen was. Increasing the prestress value has a significant effect on enhancing the initial stiffness and peak load of the box girder, but little effect on the peak displacement. For every 30% increment in prestress value, the box girder stiffness increased by 5% to 6% and the load carrying capacity improved by 6% to 8%. The increase in concrete strength also improves the bearing capacity and stiffness of box girders. For each increase in concrete grade, the stiffness of the box girder increases by 6% to 8%, and the bearing capacity increases by 8% to 9%.