OBJECTIVE：To prepare chelerythrine nanoparticles（CHE-NPs），optimize their formulation ，and evaluate its drug release behavior in vitro and its inhibitory effect on melanoma. METHODS ：Using methoxy polyethylene glycol-poly （lactic-co- glycolic acid ）（mPEG-PLGA）as carrier ，CHE-NPs were prepared by the nano-precipitation method. HPLC method and dialysis bag method were used to determine entrapment efficiency and drug loading. The formulation of CHE-NPs was optimized by Box-Behnken response surface design using overall desirability （OD）of them as dependent variables ，CHE dosage ，mPEG-PLGA concentration and poloxamer 188（F68）concentration as independent variables. The particle size and Zeta potential of CHE-NPs prepared by the optimal formulation were detected ；the characteristics of drug release in vitro were investigated ；the effects of CHE and CHE-NPs on survival rate of mice B 16 melanoma cells were compared ，and median inhibition concentrations （IC50）of them were calculated. RESULTS ：The optimal formulation included CHE of 2 mg，mPEG-PLGA of 13 mg/mL，F68 of 1.8％. Average entrapment efficiency rate of CHE-NPs prepared by the optimal formulation was （80.18±1.11）％，average drug loading was （11.36±0.28）％，average OD value was 0.96±0.04 [the relative deviation from predicted value （0.90）of OD was 6.67％]； particle size was （113.1±1.40）nm，and Zeta potential was （－21.6±0.29）mV；polydispersity index was 0.07±0.01（n＝3）； accumulative release rates of CHE control and CHE-NPs were 90.87％ and 68.68％ within 8 h，and drug release behavior in vitro of the latter was in accordance with Weibull kinetic model. Inhibitory effect of CHE-NPs on B 16 melanoma cells was significantly stronger than that of CHE ；the 24 h IC 50 of CHE-NPs and CHEwere 69.35 and 107.36 μg/mL，respectively. CONCLUSIONS ：The prepared CHE-NPs show good sustained-effect and high capacity of drug loading ，and strengthen the inhibitory effect of CHE on melanoma.