Objective:To prepare fluorouracil-loaded chitosan nanoparticle (5-Fu-CS-NP) for ophthalmologic usage and evaluate its releasing characteristics in vitro. Methods: 5-Fu-CS-NP was prepared with 5-Fu, polyacrylic acid and chitosan using dispersion method. The mean size, entrapment efficiency (EE%), drug loading (DL%) and the in vitro releasing characteristics of 5-Fu-CS-NP were investigated.Results and conclusion: The mean size of 5-Fu-CS-NP was (144.6±3.1) nm, the EE% was 84.5% and the DL% was 3.91%. 5-Fu-CS-NP had a satisfactory sustained-releasing effect and the releasing could last for 3-7 days, and the release behavior was not greatly changed within a pH value of 7.2-7.4.