In order to prolong the shelf life of millennial fruits at room temperature, chitosan (CS) and carboxymethyl chitosan (CMCS) are coated on millennial fruits by layer-by-layer self-assembly (LBL) technology. The types of force between CS and CMCS as well as the preservation effects on millennial fruits are studied. The FTIR results show that there are hydrogen bonding and electrostatic force between CS and CMCS. The CMCS/CS LBL double-layer coating film has the best fresh-keeping effects which can extend the shelf life of millennial fruits at room temperature to 9 days. The weight loss rate, decay rate, firmness, total soluble solid, Vc and organic acid content for millennial fruits after 9 days is 3.3%, 6.7%, 5.3 kg/cm2, 7.7%, 29.3 mg/hg and 0.48% respectively. The LBL multilayer coating films of CS and CMCS can effectively inhibit the transpiration and respiration strength of millennial fruits, thereby prolonging their shelf life.