Steel fibres were corroded by using the method of drying wetting cycles. Based on the investigation of their surface characters and according to the results of uniaxial tension test and finite element analysis, the effect of corrosion degrees on the deterioration of mechanical properties of corroded steel fibres was studied. Results show that many corrosion pits appear on the surface of the steel fibres after drying wetting cycles. The deterioration of mechanical properties of corroded steel fibres is due to section loss and stress concentration at these pits. Moreover, the degrees of stress concentration depend on the varying pit depth, pit width and diameter of steel fibre. Finally, the deterioration model of ultimate tensile load of corroded steel fibres, considering the effects of pit depth, pit width and diameter of steel fibre, is proposed and verified by test results. Also, the model can be adopted for calculating the ultimate tensile load of corroded steel bars.