Abstract: In this study, the nano carboxymethy starch(NCMS) was prepared by dual screw extrusion and was used as coating adhesive in micro weight coated paper(MWC). The results showed that the surface of NCMS particle was smooth and it had excellent film-forming and high film strength. The tensile strength of film can reach to 4.67 MPa,breaking elongation 26.9%. The negative charge density of NCMS is lower than that of common oxidized starch. For the paper coating formula of micro weight coated paper, when the dosage of NCMS used as the coating adhesive was 14%, the water retention properties of coating was increased evidently and the water retention value was 43.6 g/m2; the IGT printing surface strength of MWC was 0.89 m/s; the longitudinal and transverse tensile index was 47.8 and 21.7(N·m)/g separately; the ink absorption of MWC was 36.8% and 61% separately. Comparing with 20% common oxidized starch coating formulation,the water retention properties of coating was increased by 25.3%, coating viscosity was decreased by 12.4%, and the IGT printing surface strength and tensile index of MWC were improved in different degree.