【Abstract】 Objective To prepare PEGylated long circulating dacarbazine liposome（PEG-DTIC-LP）,and preliminarily study its antitumor effect in vivo. Methods The liposomes were prepared using the ammonium sulfate gradient method, and its entrapment efficiency, drug loading, morphology under electron microscope, particle size, zeta potential, stability and drug release behavior in vitro were investigated. Establish melanoma bearing mouse models. The antitumor effect of PEG-DTIC-LP was studied using mouse tumor volume, body weight and median survival time as the indicators, and DTIC solution, saline and blank liposomes were used as the control groups. Results PEG-DTIC-LP was a translucent milky white suspension with blue opalescence. The encapsulation efficiency was 60.41±2.47% and the drug loading was 5.95±0.24%. The average particle size was 190 nm, and the zeta potential was -53.8 mV. Compared with three control groups, the tumor volume of mice in PEG-DTIC-LP group was significantly smaller, and the median survival time was longer. Conclusion Long circulating liposome encapsulation is beneficial to improve the antitumor effect of DTIC.