The chloride transport characteristics of alkali-activated slag （AAS） mortars at various degrees of water saturation were evaluated comprehensively by means of conductivity tests， diffusion tests and dry-wet cycle tests. The mechanism of unsaturated chloride transport of AAS mortars was illustrated by characteristics of pore structure and moisture distribution at different degree of saturations. Results show that the conductivity and apparent chloride diffusion coefficient of AAS mortar specimens decrease significantly with the decrease of saturation. In the condition of dry-wet cycles the specimen with lower saturation has a faster chloride penetration and there is no clear chloride peak in the specimen. The influential depth of dry-wet cycles on chloride penetration is increased for the specimen of a lower saturation. The apparent chloride diffusion coefficient is lower in Na₂SiO₃ activated system than in NaOH activated system of the same saturation level， while the resistance difference of the two systems becomes smaller for a lower saturation.