Abstract: To resolve the universal contradiction between the computation accuracy and the computation efficiency in present analysis methods of box girders, the 3-D finite element analysis method of box girders with coarse mesh is proposed. Considering the deformation characters of box girders, two 8-node hexahedral hybrid stress elements with the name of 8N21β and 8N21βc are developed. The construction of the two elements is based on the modified Hellinger-Reissner variation principle with unconforming displacement functions. The 8N21β element is constructed in Cartesian coordinates and can be used for the 3-D finite element analysis of straight box girders, and the 8N21βc element is constructed in cylindrical coordinates and can be used for the 3-D finite element analysis of curved box girders. The numerical examples indicate that the two elements can yield good results under coarse mesh in the 3-D finite element analysis of box girders, and the computation efficiency can be much improved.