Aim of this paper is to present a numerical method for modeling of the so-called “equivalent box section fiber beam concrete element”. By comparing hysteresis curves of specimen of the concrete structure plotted with rebar beam with those plotted with the equivalent box section beam under a set of loading cases, the following conclusions are obtained: 1) The modeling technology of equivalent box section beam can overcome the difficulty which the rebar in beam can only be used in static calculation, and the fiber beam element can be applied to dynamic explicit analysis; 2) By comparing hysteresis curves which are plotted by the rebar beam with those obtained with model of equivalent box section beam, it is found that results are in good agreement for a specific typical loading case; 3) By comparing hysteresis curves of the equivalent box section beam with experimental data under given loading case, numerical results indicate that numerical results obtained with proposed modeling technology can fit the experiment phenomena very well.