In steel construction, beams often have to be coped at the flange to provide clearance for the framing beams or to maintain the main beam and the secondary beam at the same level. When the beams are coped, the local web buckling capacity of the beams at the coped region may be reduced. For coped beam with relatively long coped length and coped depth, elastic local web buckling may occurred. On the other hand, for coped beam with relatively short coped length and coped depth, part of the web section may yield before local web buckling occurs. Therefore, depending on the cope details, the local web buckling failure capacity of coped beam can be classified as elastic and inelastic web buckling. In this thesis, non-linear finite element analysis, which included both material and geometric nonlinearities, of the inelastic local web buckling capacity of coped steel I-beam was firstly conducted. The effects of different parameters, such as (1) web slenderness (d/tw), (2) cope depth to beam depth ratio (dc/D), (3) cope length to reduced web depth ratio (c/h0) and (4) initial imperfection of web section, to the web buckling capacity of coped steel I-beam were chosen as the main objectives to be investigated. The finite element parametric study results showed that local web buckling capacity decreased with increased initial imperfection, also with the increasing c/h0 or dc/D value. Meanwhile, the traditional elastic predictions estimated higher capacities than the results of finite element analysis for beams with short cope length and cope depth, and when the ratio of c/h0 or dc/D was smaller, the discrepancy was larger. Consequently, in order to improve this discrepancy, a hierarchical modified plate buckling formula, which considers the nonlinear reduction factor, is proposed. In general, the modified formula gives a proper conservative prediction of the local web buckling strength of a coped I beam, especially in inelastic range.