The traditional fiber element does not consider the constraint of the fixed end， which leads to the reduction of numerical simulation accuracy of reinforced concrete （RC） columns. The impact of the fixed end constraint on the damage pattern of RC columns and the simulation accuracy of the fiber unit was analyzed. 45 RC columns with a high shear span ratio in the literature were selected and the solid element models were established for numerical simulation. The results show that the modeling method is reasonable and reliable. The restraint mechanism of the fixed end and the influence of the restraint effect of the fixed end on the bearing capacity and ductility of RC columns were then explained. The control section position and its load-carrying capacity calculation method were defined， and the corresponding relation between the numerical integration point position and the control section position， and between the weight coefficient and the equivalent plastic hinge length was clarified. Finally， the formula for calculating the control section position and the equivalent plastic hinge length considering the influence of the fixed end constraint was proposed， and a fiber element simulation method considering the influence of the fixed end constraints was built. Through the numerical simulation analysis of 45 RC test columns in the literature， it is shown that the proposed method can reasonably consider the influence of fixed end constraints and has good applicability.