This paper provides a new treatment for gastric cancer with a new OMT delivery system. We synthesized MPEG-PCL, an amphiphilic polymer, to construct a nanoparticle encapsulated OMT by pH gradient method, and then examined the nanodrug's therapeutic efficacy. An integral analytical method was used to characterize the structure of MPEG-PCL. The single factor method and orthogonal test were utilized to investigate the optimum preparation process. The morphology and average size of the OMT-NPs were analyzed by transmission electron microscopy and Zetasizer. CCK-8 assay and confocal fluorescent microscope were used to study the inhibitory effect on SGC-7901 gastric cancer cells. The average size of nanoparticles was 95.86±1.54 nm. The maximum encapsulation efficiency of OMT was 46.84±4.37％, while the drug loading content was 8.89±1.09％. The cumulative release of nanoparticles was 73.07±1.5％, inspected through dynamic dialysis in vitro. Compared with free OMT, OMT-NPs showed enhanced cytotoxic effects in SGC-7901 cells. The nanoparticles could efficiently deliver the OMT into the cancer cells and release it. The OMT delivery system prepared in this paper provides a potential platform for the treatment of gastric cancer..