Abstract: To explore the effects of fiber ratio, cross-sectional shape, cross-sectional size and axial compression ratio on the torsional performance of carbon fiber reinforced polymer (CFRP)-reinforced concrete (RC) columns, this paper employs a meso-scale mechanical analysis method that can simultaneously consider the heterogeneity of concrete, the bond-slip relationship between reinforcement and concrete, and the interfacial relationship between CFRP sheets and concrete. First, a three-dimensional numerical model was established for the analysis of the torsional performance of CFRP sheet-reinforced RC columns. Subsequently, the numerical simulation results based on this model were compared with the experimental results to verify the rationality of the loading approach and the method of externally bonded CFRP sheets, and the accuracy of material parameters. Finally, based on the meso-scale mechanical analysis model, the influence mechanism of the fiber ratio, cross-sectional shape, cross-sectional size and axial compression ratio on the failure modes and mechanical properties of CFRP sheet-reinforced RC columns under torsion was investigated. Results show that the torsional bearing capacity of RC columns increases with the increase of fiber ratio, but the improvement rate decreases with the increase of fiber ratio. Influenced by the distribution of confining pressure, the effective restraint area of the circular section is larger than that of the square section, making the restraint effect of CFRP sheet on the circular column better than that of the square column. The size effect can be observed in the nominal torsional strength of CFRP sheet-reinforced RC columns. The torsional bearing capacity firstly increases and subsequently decreases with the increase of the axial compression ratio, and reaches its maximum capacity at n=0.4. Furthermore, a calculation formula for the torsional bearing capacity of FRP sheet-reinforced RC members is proposed by superposing specification formulas. Compared with the numerical simulation results in this paper, the formula can give a design value of safety redundancy of 30.2%, which can be initially used for the safety design of torsional bearing capacity of CFRP sheet-reinforced RC columns.