Methotrexate (MTX)-encapsulated polymeric micelle of methoxy poly(ethylene glycol) (MPEG)-grafted chitosan (ChitoPEG) copolymerwas prepared by mixing of MTX/DMSO solution into ChitoPEG/deionized water. MTX-encapsulated polymeric micelle of chitoPEG has spherical shapes particle size around 50nm at TEM observation. In 1H NMR study, the specific peaks of MTX and ChitoPEG was observed at polymeric micelle in DMSO while MPEG peaks only obtained at D2O, indicating that MTX/chitosan main chain composed of inner_core and MPEG composed of outershell. Resultantly, MTX was incorporated into ChitoPEG copolymer via ion complex formation between MTX and chitosan main chain.