Background and Aims: The incidence of diabetes mellitus has reached an alarming level. Cardiovascular disease (CVD) is the leading cause of mortality in diabetic patients. However, the association between ratio and survival outcomes in patients with diabetes mellitus (DM) and new-onset acute coronary syndrome (ACS) remains unknown. This study aimed to assess the association between the TG/HDLC ratio and the risk of death in diabetic patients with new-onset acute coronary syndrome in the Han Chinese population. Methods: Data in this study were retrospectively collected from January 2016 to December 2016 from patients with type 2 diabetes mellitus (T2DM) and new-onset ACS in Tianjin Chest Hospital. Patients were classified according to the baseline TG/HDLC ratio. Kaplan-Meier survival curves were used to demonstrate survival outcomes. Univariate and multivariate Cox proportional risk regression analyses were used to evaluate the hazard ratios and 95% confidence intervals (CIs) for the risk of death. Subgroup analysis was used to determine the presence of any interaction. Results: In total, 152 patients died, 98 of them from heart disease. The Kaplan-Meier survival curve showed that there were no significant differences for both all-cause and cardiac mortality between Median 1 and Median 2 in log-rank test. Multivariate Cox regression analyses revealed that the adjusted hazard ratio increased significantly (p 0.05) with increasing median TG/HDLC for not only all-cause mortality and cardiac death, but also nonfatal stroke, fatal stroke and fatal MI. The association between the TG/HDLC ratio and the risks of all-cause mortality and cardiac death in diabetic patients with new-onset ACS was similar among subgroups (p > 0.05). Conclusions: An elevated TG/HDLC ratio (TG/HDLC >1.522) is associated with an increased risk of all-cause and cardiac death risks in diabetic patients with new-onset ACS. Therefore, TG/HDLC ratio may be a beneficial parameter to evaluate the prognosis of this high-risk population.