In the process of alumina production, a large amount of strong alkaline waste residue - red mud will be produced. Red mud is rich in calcium, silicon, aluminum and other elements, and can be added to concrete as a mineral admixture to replace cement. Efficiency evaluation theory is widely used to evaluate the efficiency of mineral admixtures in concrete, but it has not been used to evaluate red mud. In this study, in order to fill the relevant gaps, a series of mortar mixtures with water-binder ratios of 0.3, 0.4, and 0.5 and red mud replacement rates of 0%, 5%, 10%, 15%, 20%, 25%, and 30% were prepared. The compressive strength test and chloride ion natural penetration test were carried out, and the gelling efficiency factor and durability efficiency factor of red mud were calculated. The existing results show that the cementitious efficiency factor and the durability efficiency factor of red mud are affected by the water-binder ratio and the red mud replacement rate. When the red mud replacement rate was higher than 20%, the 0.3 water-to-binder ratio showed better gelation efficiency, on the contrary, when the red mud replacement rate was lower than 20%, the 0.4 water-to-binder ratio showed better gelation efficiency. The durability efficiency of red mud increases with the increase of red mud replacement rate. To sum up, by reasonably controlling the water-binder ratio and the replacement rate of red mud in the mortar mixture, the durability of the mortar mixture against chloride ions can be improved with little change in the gelling efficiency.