This paper is focused on investigating the corrosion behaviour of steel-reinforced alkali-activated mortar (AAM) across five different mixed ratios of slag/fly ash. To accelerate the chloride-induced corrosion, alternative wetting-drying cyclic corrosion was employed by using the corrosive environmental chamber. Electrochemical measurements, including half-cell potential, linear polarisation resistance and Tafel extrapolation method, were utilised to evaluate the corrosion resistance parameters of different corroded samples. The evolution of corrosion potential and linear polarisation resistance along with time was recorded daily, while the Tafel constant B values were recorded in passive condition (before corrosion) and active condition (after corrosion) respectively. The free and bound chloride content at the steel-AAM interface at the corrosion initiation was obtained, together with SEM-EDS analysis at the steel-AAM interface. The results show that the determination criteria of corrosion probability from ASTM C876 cannot be directly used for reinforced AAM. Accordingly, an adaption from ASTM C876 about the corrosion criteria for reinforced AAM is proposed. Moreover, the results suggest Tafel constant B should be 22mV (in comparison to 52mV for OPC) and 54 mV (in comparison to 26mV for OPC) for passive and active conditions, respectively.