Objective To evaluate the relationship between gastrocnemius and type 2 diabetes mellitus (T2DM) complicated with sarcopenia by conventional ultrasound and shear wave elastography (SWE). Methods 112 patients with T2DM were selected from our hospital from January 2020 to January 2023. According to the diagnostic criteria for sarcopenia by the Asian Working Group for Sarcopenia (AWGS), the patients were divided into T2DM group and T2DM complicated with sarcopenia group. The muscle thickness, feathery angle and muscle bundle length of the medial head of the right gastrocnemius were measured by conventional ultrasound. Young"s modulus and shear wave velocity (SWV) of gastrocnemius muscle was measured by SWE. Univariate and multivariate binary Logistic regression were used to analyze the correlation between clinical and ultrasonic features for T2DM complicated with sarcopenia. Results Univariate analysis showed that the duration of diabetes in T2DM patients complicated with sarcopenia was longer than that in T2DM group, and the content of glycosylated hemoglobin was higher than that in T2DM group. Among renal function parameters, more patients with increased creatinine and urinary protein, and decreased eGFR in T2DM complicated with sarcopenia group, with statistical significance (P < 0.05). The results of ultrasonic measurements of gastrocnemius muscle showed that the thickness, feathery angle, muscle bundle length, Young"s modulus and SWV in T2DM complicated with sarcopenia group were lower than those in T2DM group, and the differences were statistically significant (P < 0.05). Multivariate binary Logistic regression analysis showed that creatinine level (OR = 1.434; 95 CI OR: 1.023~2.011, P = 0.036), muscle bundle length of gastrocnemius (OR: 0.917; 95 CI OR: 0.857~0.981, P = 0.0126), muscle thickness of gastrocnemius (OR = 0.794; 95 CI OR: 0.668~0.944, P = 0.009), Young"s modulus (OR = 0.678; 95 CI OR: 0.530~0.868, P = 0.002) and SWV of gastrocnemius (OR = 0.484; 95 CI OR: 0.299-0.785, P = 0.003) was independently correlated with T2DM complicated with sarcopenia. The area under ROC curve was 0.936 (95%CI: 0.890-0.981), the sensitivity was 82.95%, and the specificity was 95.83%. Conclusion The decrease of Young"s modulus and SWV value, thickness and shorter bundle length of gastrocnemius measured by conventional ultrasound and SWE, and decreased renal function may indicate that T2DM patients are complicated with sarcopenia. Conventional ultrasound combined with SWE and decreased renal function can help clinicians identify T2DM with sarcopenia at an early stage, and provide auxiliary information for intervention and improvement of patient prognosis.