Objective To investigate the influence of long-term exposure to oil and gas toxicants on the peripheral blood T lym-phocyte subsets in Karamay Uygur and Han refining workers and the underlying mechanism.Methods 175 cases of Uighur and Han refinery workers who had long-term close contact with poison of oil and gas(112 cases of Han people and 63 cases of Uygur people)and 110 healthy people(70 cases of Han people,40 cases of Uighur)were selected as research subject.The peripheral blood T lymphocyte subsets of all cases were detected for comparative analysis.Results Compared with healthy control group,the median of CD4+in the uighur refinery workers was significantly reduced(P<0.05);the CD8+in Han ethnic refinery workers was signifi-cantly lower,while the ratio of CD4+/CD8+increased significantly(P<0.05).Compared with Han ethnic,the median of CD3+, CD8+in uighur significantly increased,while the ratio of CD4+/CD8+decreased significantly(P<0.05).Conclusion Long-term close contact(more than 5 years)of oil and gas poison will significantly reduce the function of peripheral blood T lymphocyte sub-sets of refinery workers,and the effect on Han ethnic oil refinery workers was significantly higher than that on Uighur,,so corre-sponding measures on effective occupational protection are necessary to carry out.