In this work, a numerical model is proposed to study chloride transport in alkali-activated materials. This model is based on multiple-relaxation-time lattice Boltzmann method, where particle distribution function is introduced to simulate the chloride binding and diffusion. This model takes into account diffusion, homogenous reaction between chloride ions and diffusive solid, and heterogeneous reaction between chloride ions and non-diffusive solid. The accuracy of the model is confirmed by a benchmark simulation of transient reactive transport problem. As a demonstration, this model is then applied to simulate chloride transport in alkali-activated slag paste with varying alkaline activators. The influence of alkali content, silica content, curing age and chloride binding on the chloride transport property is briefly discussed.