Abstract: Shear lag effect has significant effect on stress and deflection of composite beams. According to the elastic analytical model of composite beams, stress and deflection analytical solutions for the cases of simply supported composite beams and cantilever composite beam under uniform distribution load and concentrated load are derived by ignoring slip effect in the interface. By introducing effective flange width and effective sectional rigidity, practical design methods for considering shear lag effect of composite beam are presented, and the results calculated by these methods have good agreement with those obtained from analytical solutions. By comparing different design methods for composite beam considering shear lag effect from different countries, the simple practical design method presented in this research is found to have high accuracy despite of its simplicity.