Objective: To analyze the effect of decitabine combined with conventional chemotherapy on myelodysplastic syndrome (MDS) and its influencing factors. Methods: Eighty patients with MDS who were admitted to our hospital were selected by this study between February 2017 and February 2018. The selected patients were divided into a traditional group (CAG/DA scheme) and the combined group (DAC combined with CAG/DA scheme) according to the random number table method, 40 each. The clinical treatment effects of the two groups were compared, and the influencing factors of the effect were analyzed. Results: After four courses of treatment, the difference in the total effective rate between the two groups were statistically significant (P<0.05); the difference in the incidence of adverse reactions and in the overall survival (OS) rate between the two groups were not statistically significant (P>0.05). However, the progression free survival (PFS) rate of the combined group was significantly higher compared with the traditional group (P<0.05); the Hb level, WHO stage and and karyotype of the patients before treatment had significant influence on the treatment effect (P<0.05). Conclusion: DAC in combination with conventional chemotherapy has good effect in the treatment of MDS, and it will not increase adverse reactions. In addition to treatment scheme, the influencing factors of the effect of treatment for MDS also include Hb, WHO stage and karyotype. doi: https://doi.org/10.12669/pjms.36.5.2289 How to cite this:Liu T, Wang J, Li C, Jia L. Clinical effect of decitabine in the treatment of myelodysplastic syndrome and influencing factors. Pak J Med Sci. 2020;36(5):1084-1088. doi: https://doi.org/10.12669/pjms.36.5.2289 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.