This research aimed to create analytical models to approach experimental tests result of the single-story steel infilled frame. Model validations were done on previously studied test results of five specimens. Stress-strain parametric curve of steel and infill wall masonry were approached by constructing multiple straight lines to obtain lateral load stages and modulus of elasticity. Number of lateral load stages and elasticity modulus changes then were applied to analytical models to yield lateral load-displacement curve. Those curve-fitting approach are monitored until the curves of lateral load-displacement are resembling to the experiments. Six load stages are obtained and applied to all analytical models resulting average differences of displacement value on each load stages for model SW, PW1, PW2, PW3, and PW4 are 5.2 mm, 1.3 mm, 1.6 mm, 1.5 mm, and 1.0 mm, respectively. Considering the high nonlinearity of the infill wall, the results from the analytical models have closely approximated those of the experiment. Analytical models that are derived from this study could be used to determine equivalent diagonal strut width for further analysis on steel infilled frame building structures.