Elastic lateral-torsional buckling (LTB) strength of tapered I-girders with corrugated webs under uniform moment is investigated. The finite element (FE) program using beam elements is developed to study LTB behaviors. The results from this program are compared with those from the commercial software ABAQUS using shell elements. From the comparisons, it is found that the developed FE program's results agree well with the results from ABAQUS. The closed-form equation for the critical buckling moment of the tapered I-girder with corrugated webs under uniform moment is proposed for design purpose based on the results from the developed FE program. The proposed equation increases efficiency in bridges and buildings design.