Abstract: In order to explore the effect of left-behind children’s perceived teacher emotional support on school adjustment, and the mediating role of basic psychological needs and positive emotions in between, 1371 left-behind children were investigated using Middle School Students’ Perceived Teacher Emotional Support Scale, School Adjustment Scale, Basic Psychological Needs Scale, Positive Emotions Scale. The results showed that: 1) perceived teacher emotional support was positively related to basic psychological needs, positive emotions and school adjustment; 2) perceived teacher emotional support can positively predict school adjustment;3) perceived teacher emotional support affects school adjustment indirectly through three paths: through the independent mediating roles of basic psychological needs; through the independent mediating roles of positive emotions, and through the chain mediation of basic psychological needs and positive emotions. The study reveals the effect and action mechanism of the left-behind junior high students’ perceived teacher emotional support on school adjustment, which is of some realistic value in promoting students’ school adjustment and preventing the emergence of maladjustment in schools.