Objective To study the preparation of polylactic-co-glycolic acid(PLGA) nanoparticles carrying arsenic trioxide(As_(2)O_(3)).Methods Polymer PLGA was used to prepare arsenic trioxide nanoparticles with w/o/w double-emulsion evaporation technique,which was optimized by uniform design test.Results The shape of As_(2)O_(3)-loaded PLGA nanoparticle was round,the size was well-distributed,the mean diameter was 178.2 nm,the average encapsulation ratio reached 53.19%,and the average drug loading was 0.64%.Conclusion The technique to prepare nanoparticles is simple and the quality can be easily controlled.