Objective: To investigate the anti-inflammatory effect of the protein derived from the soluble factor of Heligmosomoides polygyrus (H. polygyrus) excretory-secretory in a colitis model. Methods: Colitis was induced by providing drinking water containing 3% dextran so- dium sulfate (DSS) for a week. DSS was administrated in a cycle protocol, each cycle consisted of 7 days of 3% DSS in the drinking water and followed by 7 days of regular water. This study consisted of five treatment groups, including Groups A (control) received untreated water, B (DSS only, without excretory-secretory), and C–E injected (i.p.) with excretory-secretory protein (H. polygyrus excretory-secretory total, excretory- secretory 28 kDa and excretory-secretory 55 kDa, respectively). Mice received injection every week. The injection of excretory-secretory was started from the 6th weeks and continued until 11 weeks. At the end of 11 weeks of the experiment, mice were sacrificed, colon tissue was removed and then subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, flow cytometry, real-time PCR and histology examination. Results: Mice received H. polygyrus excretory-secretory 55 kDa reduced mono-nuclear cell infiltrations. H. polygyrus excretory-secretory 55 kDa induced the down-regulation of mRNA interferon- γ expression. There were significant differences in the expression of mRNA interferon in the colon of mice after the administration of the excretory-secretory 55 kDa protein fraction compared with other groups (P < 0.001), whereas mRNA transforming growth factor- ß expression up regulated in the colon of mice after the administration of the excretory-secretory 55 kDa protein fraction compared with total excretory-secretory group (P < 0.05). The treatment of colitis in mice with excretory- secretory 55 kDa protein fractions modulated interleukin-10 (IL-10) expression, whereas excretory-secretory total and excretory-secretory 28 kDa protein fractions insufficient promoted IL-10 expression. Excretory-secretory 55 kDa proteins fraction promoted IL-10 expression via Foxp3-independent pathways. Conclusions: Excretory-secretory 55 kDa protein could reduce inflammation and have potential therapy. H. polygyrus excretory-secretory 55 kDa was the soluble factor that may help in the development of novel treatments to cure colitis.