Abstract: The effective length factor of columns of the drive-in storage racks in the cross-bay direction is affected by many factors. For the simplified column model with a top displacement constraint and a bottom torsional restraint, the calculation formulas of the elastic buckling load are derived. The calculation results show that, when the rigidity of restraint is at a low level, the change of rigidity has significant effect on the effective length factor of columns. Then the elastic buckling load of models about one line of columns is studied by the finite element analysis to obtain the effective length factor of columns. The existence of rail beams and uneven load distribution can increase the elastic buckling load of models. Finally, based on the numerical results, simplified calculation formulas for the length factor are proposed to calculate the column effective length factor of any rack with certain rotational stiffness of column base and lateral stiffness of bracing system.