Circadian rhythm is essential to human physiological homeostasis and health. The oscillation of host circadian rhythm affects the composition and function of intestinal microbiota, meanwhile, the normal operation of host circadian rhythm depends on the diurnal changes of intestinal microbiota. The imbalance of intestinal micro-ecology or the disorder of host circadian rhythm may lead to psychiatric disorders, while the intervention of plant polysaccharides is a possible way to alleviate circadian rhythm disturbance and the related psychiatric diseases. This review discusses the interaction between host circadian rhythm and intestinal microbiota and their effects on psychiatric disorders, and proposes a possible strategy of plant polysaccharides to alleviate circadian rhythm disorders and related psychiatric disorders by regulating intestinal micro-ecology.