In this study, low carbon steel fibres were corroded to various corrosion degrees by cycling in 3.5% NaCl solution and 60 °C oven, and by applying a designed current density of 20 mA/cm2. Then the corrosion characters and corrosion degree on tensile strength of the two types of corroded steel fibres were investigated. It was found that the cycles induce pitting and the current induces relatively uniform corrosion. The results of tensile test show that the actual tensile strength of steel fibres was reduced in the case of pitting, while it was marginally affected by uniform corrosion. As the corrosion degree increased, both of the nominal tensile strength and elongation of the two types of corroded steel fibres decreased. In addition to weight loss, local section loss at the pits is the main reason for further degradation of the mechanical properties of steel fibres and gives a brittle failure.