Abstract: The torsion and bending capacity of RC torsion-bending components are calculated separately according to the methods of pure torsion and bending in GB50010-2002, which is contrary to test results and cannot reflect a force state. Therefore, the computing model of the code formula is inaccurate, which causes low reliability and the demand of GB50068-2001 cannot be satisfied. Through the analysis of existing test data, a modified formula based on 1/4 arc and its calculation method are proposed. The overall force correlation of torsion and bending is considered in this formula, with a definite physical meaning. The calculated reinforcement area can be returned to this formula for checking. Computational results show that the computing model of the modified formula is more accurate and its reliability can meet the demand of GB50068-2001.