Background: In recent years, cardiometabolic index (CMI) has been introduced to predict the risk of diabetes in the general population and is also strongly associated with cardiovascular disease, hypertension, and ischemic stroke, but the relationship between CMI and diabetic microalbuminuria remains unclear. This study intends to investigate the relationship between CMI and microalbuminuria in patients with type 2 diabetes mellitus(T2DM). Methods: 524 subjects (mean age 57.28 ± 10.52 years, 283 males and 241 females) from the Department of Endocrinology, Southwestern Medical University Hospital, China (data collected from June 2017 to June 2019) participated in this study. CMI was calculated by triglyceride to high-density lipoprotein cholesterol ratio(TG/HDL-C) multiply waist-to-height ratio(WHtR). Microalbuminuria was identified by the urinary albumin‐to‐creatinine ratio (UACR) when the value was between 30–300 mg/g. Multivariate logistic regression aimed to explore the association between CMI and diabetic microalbuminuria; The receiver operating characteristic (ROC) analysis was employed to evaluate the predictive value of CMI for microalbuminuria in T2DM patients. Results: The prevalence of microalbuminuria in all participants was 37.8% in men and 41.1% in women. Regardless of gender, CMI was significantly more unfavorable in the microalbuminuria group. The incidence of microalbuminuria increased dose-responsively with increasing CMI quartiles. Modeling CMI as a continuous variable in a multivariate-adjusted model, we observed an independent effect of each 1 SD increase in CMI on the risk of developing microalbuminuria. The relationship was more pronounced in women than in men. In women, the odds ratio(OR) for microalbuminuria was 5.666 (95% CI: 2.247-14.289) in the highest quartile of CMI compared with the lowest quartile; in men, the OR was nearly 4-fold increased(OR: 4.667, 95% CI: 1.910-11.405) in the same situation. The AUC for CMI was 0.681 (0.613 to 0.749) in women and 0.648 (0.582-0.713) in men. Conclusion: High levels of CMI were independently associated with diabetic microalbuminuria, and CMI, a novel index covering lipids and central obesity, explained the gender differences in obesity-related microalbuminuria excretion, an effect that was substantially increased in women. The results of this study provide important insights into the potential usefulness and clinical relevance of CMI for microalbuminuria in Chinese patients with T2DM.Registration number: ChiCTR2100047930Date of registration: On June 27, 2021 (retrospectively registered)