AIM: To investigate the curative effect of erythromycin in the treatment of ureaplasma mycoplasma pneumonia and its influence on cell subset and liver function. METHODS: Forty-one cases of children patients with ureaplasma mycoplasma pneumonia that accepted from May 2016 to May 2017 were selected as experimental group. The children patients were given 10 mg/kg erythromycin and suitable amount of 5% glucose injection by intravenous infusion, twice per day, treatment for 7-10 days. Forty-one cases of healthy check-up newborns were selected as healthy group at the same time. Cell subsets and liver functions were compared between the healthy group and the experimental group before and after treatment, and the efficacy and safety in the experimental group were analyzed. RESULTS: Before treatment, the CD4+, CD4+/CD8+ of experimental group were (41.95±5.71)% and 1.26±0.18, which were lower than those in the healthy group of (48.13±7.21)% and 1.79±0.20.The CD8+ in experimental group was (35.10±4.41)%, which was higher than that in the healthy group (26.56±3.13)%, alanine aminotransferase, lactate dehydrogenase, total bile acid, bilirubin, total cholesterol, triglycerides, aspertate aminotransferase, Alt/aspertate aminotransferase in the experimental group were (136.71±17.20) U/L, (439.67±54.45) U/L, (28.39±3.72) U/L, (68.05±8.95) μmol/L, (7.82±0.95) mmol/L, (1.70±0.24) mmol/L, (113.37±14.25) U/L, 1.24±0.14, respectively,which were higher than those in the healthy group of (45.26±4.88) U/L, (397.98±47.20) U/L, (22.24±2.66) U/L, (36.71±4.83) μmol/L, (4.26±0.46) mmol/L, (1.24±0.17) mmol/L, (62.51±9.19) U/L, 0.77±0.12. After treatment, the levels of CD4+ and CD4+/CD8+ in the experimental group were significantly increased and the levels of CD8+, alanine aminotransferase, lactate dehydrogenase, total bile acid, bilirubin, total cholesterol, triglycerides, aspertate aminotransferase, alanine aminotransferase /aspertate aminotransferase in the treatment group were significantly decreased. However, there were no significant differences of those items between the two groups (P>0.05). CONCLUSION: Erythromycin has positive therapeutic effect on ureaplasma mycoplasma pneumonia, it helps cell subgroup and relieves liver function.