Based on the study of selective leaching process of lithium slag（LS） in alkaline solutions， the leaching ratios of Si， Al and Ca in LS under different alkali-hydrothermal conditions were calculated， the phase composition， hydration product types and micro-morphology of LS before and after alkali-hydrothermal treatment were analyzed. Meanwhile， the pozzolanic activity of LS and the reaction behaviors among dissolved components in LS were investigated. The results show that the increase of NaOH solution molarity is beneficial to the dissolution of spodumene and the leaching process of Si， Al and Ca. Temperature and leaching time are the main factors affecting the reaction process of alkali-activated lithium slag （AALS）. In the alkali-hydrothermal environment above 60 ℃， the pozzolanic activity of LS can be effectively activated， and the leaching ratios of different elements in LS are obviously increased， accompanied by the formation of a large number of reaction products.