Purpose: Muscle dysfunction is considered as a sign of poor prognosis in patients with type 2 diabetes (T2D). Thus, early detection of muscle disorders is particularly important in T2D population. For free fatty acid (FFA) is known as a clinical indicator of metabolic diseases and muscle function, hence, we aimed to investigate whether FFA could serve as a biomarker for muscle function.Methods: There are totally 160 adult subjects with T2D were characterized and analyzed in this study. Muscle mass and function were measured by walking speed, grip strength and height-adjusted appendicular skeletal muscle mass (SMI). Logistic regression was applied to explore the correlation of FFA with muscle indicators. Receiver operating characteristic (ROC) curves were utilized to conduct the diagnostic value of FFA.Results: FFA was negatively correlated with SMI (r = -0.347, P = 1.0E-05), grip strength (r = -0.313, P = 7.1E-05) and walking speed (r = -0.167, P = 0.039). Notably, the relationships between FFA and SMI and walking speed remained significant even after adjusting for age, sex, body mass index (BMI) and hemoglobin A1C (HbA1c). The combination of conventional indicators including age, BMI and HbA1c provided discrimination effect of low grip strength with an AUC of 0.648, low walking speed with an AUC of 0.714. Importantly, when FFA was added to the model, the value of ROC curve was further improved, with an AUC of 0.785 for low grip strength, 0.755 for low walking speed.Conclusions: The current study demonstrated a negative correlation of FFA with muscle indicators in adult T2D patients after adjusting for HbA1c. FFA may play an important role in the pathological process of muscle dysfunction in adults with T2D.