Purpose: The purpose of this study was to explore the changes in macular thickness (MT) in normal people, patients without obvious diabetic retinopathy (NDR) and patients with nonproliferative diabetic retinopathy (NPDR) and to study the possible risk factors for Methods: Thirty-one healthy individuals, 40 people with no sign of DR and 60 people with mild NPDR were included in this crosssectional study. All patients underwent a complete ophthalmological examination. Optical coherence tomography (OCT) was used to measure the MT of each participant. The potential relationship between MT and systemic risk factors for DR, including diabetes duration, body mass index (BMI), hemoglobin A1c (HbA1c), serum lipids, and blood pressure, was analyzed. Results: The MT of the right and left eyes in the central and inner ring regions of the NPDR group and NDR group were significantly different from that in the control group. The MTs of the right and left eyes in the central region and inner ring region were also significantly different between the NPDR group and NDR group, but the MTs of the right and left eyes in the outer ring region were not significantly different among the three groups. Diabetic duration, total cholesterol (TC), triglycerides (TGs), systolic pressure, and diastolic pressure were positively correlated with the MT of the right and left eyes in the central region. Conclusion: MT increases, especially in the central region and inner ring, may be the first structural retinal change in diabetic patients and is related to the duration of diabetes, TC, TG, systolic pressure and diastolic pressure.