Mango is known as the "king of tropical fruits" for its unique flavor and rich nutrition. However, mango is extremely perishable during postharvest ripening, and the decay loss caused by anthracnose is the most serious. Therefore, how to prevent and control mango anthracnose after harvest has become a bottleneck problem restricting the healthy development of mango industry. In this paper, Tainong No.1 mango was used as the experimental material, and the green cinnamon essential oil composite chitosan lotion was used as the treatment means to study its control effect and mechanism on postharvest mango anthracnose, which would provide theoretical basis and practical reference for the development of postharvest mango storage, transportation and preservation industry in China. The results showed that the treatment of 0.5% cinnamon essential oil+0.3% chitosan had the best control effect on mango anthracnose, the treatment of 0.03% cinnamon essential oil could completely inhibit the growth and spore production of mango anthracnose in vitro, and the treatment of 0.01% and 0.02% cinnamon essential oil had obvious destructive effect on mango anthracnose mycelium. The complex treatment significantly inhibited the expansion of mango anthracnose disease spot, increased the content of disease resistance related substances lignin, total phenol (TP) and hydrogen peroxide (H₂O₂), and increased the content of disease resistance related enzymes phenylalanine ammonia lyase (PAL), peroxidase (POD),β-1,3 glucanase (β-1,3-GA) and chitinase (CHI). It can be seen that cinnamon essential oil composite chitosan lotion has a good control effect on mango anthracnose by inhibiting or destroying the growth and spore production of mango anthracnose mycelium, and inducing mango fruit to improve disease resistance. Therefore, the proper concentration of cinnamon essential oil combined with chitosan lotion treatment would provide a new green way to control mango anthracnose after harvest.