This study aims to see whether there is an effect of ozone therapy on the wound healing phase of diabetic ulcers in patients with diabetes mellitus at Al Huda Woundcare Clinic Lhokseumawe City in 2016. This research is quassy experiment with samples in this study amounted to 20 patients diabetes mellitus at Al Huda Woundcare Clinic Lhokseumawe City. This research was conducted from 04 until 18 October 2016. Sampling by total sampling method. The analysis used paired t-test (dependent). The result of this research is the age of patient of diabetes mellitus patient at Al Huda Woundcare Clinic of Lhokseumawe city most of the aged between 56-65 years as many as 12 respondents (60,0%) and gender of patient of diabetes mellitus mostly female are 11 respondent (55,0%). The result of paired t test is obtained p-value 0.000 <α = 0,05. This shows that there is influence of ozone therapy to phase wound healing diabetic ulcer in patient of diabetes mellitus at Al Huda Woundcare Clinic of Lhokseumawe City 2016. The results of this study can provide benefits for the community, especially reponden that as an input that ozone therapy can serve as a new treatment alternative in addressing the problems of diabetic wounds with modern wound care so convincing to the public that diabetic wounds can be cured.