Objective: To describe the levels of residual β-cell function in patients with newly-onset type 1 diabetes mellitus, and investigate factors that may be related. Methods: Data obtained from 105 newly-onset hospitalized type 1 diabetes mellitus patients in the First Affiliated Hospital of Nanjing Medical University from 2010 to 2015. Hemoglobin A1c, islet autoantibodies and HLA-A-DR haplotypes were tested. Mixed-meal tolerance test was carried out until the fasting blood glucose was lower than 10 mmol/L; blood glucose, insulin and C-peptide were measured during the test. The rates of peak C-peptide ≥ 0.2 nmol/L were calculated and logistic regression analyses were performed to explore the influence factors. Results:Eighty-night point five percent of patients had peak C-peptide ≥ 0.2 nmol/L. Logistic regression analyses suggested that factors including age of onset ≤18（OR 0.08，95% CI 0.01~0.90），diabetic ketosis or ketoacidosis onset（OR 0.08，95% CI 0.01~0.83），High-risk HLA-A-DRB1 haplotypes（OR 0.07，95% CI 0.01~0.61），counts of islet autoantibodies >2（OR 0.10，95% CI 0.01~0.87） were related to lower rates of peak C-peptide ≥ 0.2 nmol/L. Conclusion: We found that residual β-cell function exists in patients with newly-onset type 1 diabetes mellitus. These data reinforce the inadvisability of using C-peptide alone to differentiate between type 1 diabetes mellitus and other forms of diabetes. We also found that age of onset, diabetic ketosis or ketoacidosis onset, HLA-A-DRB1 haplotypes and islet autoantibodies were associated with β-cell function in patients with newly-onset type 1 diabetes mellitus.