As a new type of steel-concrete composite structure, the prestressed concrete(PC) box girder with corrugated steel webs is widely used in box girder bridges all over the world. There were no bending vibration frequency formulas for this new type of structure in the current codes of China. In order to find the vibration frequency analytical formulas of the continuous composite box girder with corrugated steel webs, the governing differential equations and corresponding natural conditions of the bending vibration frequency were established by means of the energy variation principle and Hamilton principle. The bending vibration frequency formulas of the two-span continuous box girder with corrugated steel webs were obtained. In the formula, it was found that the influence factors of bending vibration frequency can be divided into three aspects: shear lag, shear deformation of corrugated steel webs, and the coupling relationship. Combined with the results of the finite element analysis and the indoor model test, the validity of the formulas were proven. The analysis results show that the effects of the coupling relationship and shear lag have low influences on the bending vibration frequency of the box girder with corrugated steel webs, while the shear deformation of corrugated steel webs has great influence.