Steel reinforced concrete (SRC) cross beam has high stiffness and seismic resistance capability, but it is difficult to determine a reasonable beam span-height ratio in engineering applications because there is no general theory in this area. In this paper, we developed a numerical model for SRC cross beam deflection simulation, in which the effect of cast-in-situ concrete floor on the beam has been taken into consideration as an effective flange of the beam. We also investigated the effect of the beam cambering limits in construction on beam deflection under different span-height ratios. The numerical results shows that seismic action and wind load have little effect on the span-height ratio, while beam cambering in construction is very favorable to decrease beam deflection. In addition, steel stiffness has great influence on the deflection of cross beam, and elastic deflection is only one fourth of the actual deflection. Therefore, the reasonable span-height ratio of SRC cross beam should be 20 to 30.