Aim To measure left atrial (LA) phase function and heart rate variability (HRV) in patients with asymptomatic diabetes by tissue Doppler echocardiography. The correlation between LA phase function and HRV was evaluated. Methods 158 patients with type 2 diabetes mellitus (diabetes mellitus group, n=158) with normal blood pressure and without clinical symptoms and 120 healthy persons with normal blood and pressure and without cardiovascular diseases (control group, n=120) were selected. Left atrial total emptying fraction (LATEF), left atrial passive emptyingvolum (LAPEF), left atrial active emptying fraction (LAAEF), global longitudinal strain (GLS), early diastolic velocity of left atrial strain rate and late diastolic velocity of left atrial strainrate were measured by tissue Doppler echocardiography. Standard diviation of NN intervals (SDNN), root mean square successive difference (rMSSD), percentage of adjacent R-R intervals that varied by more than 50 ms (p50NN), time domain HRV index and low frequency domain 24 h (LF), high frequency domain (HF) and total power (TP) were measured by multifunctional electrocardiograph. The difference of above indexes between diabetic group and control group were compared. Univariate and multivariate Logistic were used to evaluate the correlation between HRV and LATEF, GLS and other LA temporal functional indicators. Results LATEF (t=5.167, P<0.1) and LAPEF (t=21.486, P<0.1) were significantly lower in the diabetic group than in the control group. LAAEF (t=8.467, P<0.1) was significantly higher than in the control group. The SDNN, rMSSD, p50NN, LF, HF and TP in the diabetic group were significantly lower than in the control group (all P<0.1). Multivariate Logistic regression analysis showed that LATEF was independently correlated with HbA1c (OR=0.2,5%CI:0.239～0.633, P=0.7), LVMI (OR=0.0,5%CI:0.195～0.608, P=0.3) and 24h LF (OR=0.7,5%CI:1.486～3.812, P<0.1). GLS was independently correlated with HbA1c (OR=0.7,5%CI:0.380～0.782, P=0.023), LVMI (OR=0.2,5%CI:0.971～0.999, P=0.3), E/e′(OR=0.4,5%CI:0.255～0.486, P=0.039) and 24h LF (OR=6.1,5%CI:4.330～10.097, P<0.1). Conclusions LA phase function and autonomic function are significantly impaired in asymptomatic diabetic patients. The LA storage function, catheter function, and auxiliary pump function as assessed by volume and strain methods are significantly affected by diabetes. These findings may partially explain the increased cardiovascular morbidity and mortality in atrial fibrillation in diabetic patients.