Objective: To investigate the correlation between pre- insulin therapy period (the time from definite diagnosis to initiation of insulin therapy), insulin therapy period and the intima-media thickness of common carotid artery (CCA-IMT) in patients with type 2 diabetes by means of color Doppler ultrasonography (CDU). Methods: Two hundred and fifty-two patients with type 2 diabetes were included in this study, 138 were male and 114 were female, their age ranged from 22 to 87 (mean 59 ± 14) years; the course of disease was 1 to 43 (mean 9.3 ± 3.3) years; The duration of insulin therapy was 0 to 20 (mean 4.2 ± 1.5) years; and pre- insulin therapy period was 0 to 43 (mean 7.1 ± 2.3) years. The CCA-IMT was detected with two-dimensional high-frequency ultra sonography. The mean value of bilateral CCA-IMT was calculated. The possible risk factors [age, duration of insulin therapy, pre- insulin therapy period, fasting blood glucose, glycosylated hemoglobin, triglyceride, total cholesterol (TCH), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C)] that might impact CCA-IMT were analyzed with multiple linear regression, and their risk factors were identified. Partial correlation analysis was used to control the impact of risk factors on CCA-IMT. The relationship between the pre- insulin therapy period, insulin therapy period and CCA-IMT were observed. Results: Circled digit oneAge, LDL-C level and pre- insulin therapy period were linearly related to CCA-IMT (standardized coefficients Beta = 0.580, 0.242, and 0.195, respectively, P < 0.05). The regression equation was Y = 0.241 + 0.008 X1 + 0.060 X2 + 0.005 X3 (X1 = age, X2 = LDL-C, X3 = pre-exogenous insulin period). Circled digit twoAfter controlling the above risk factors, the pre- insulin therapy period and the mean value of CCA-IMT showed a linear positive correlation (r = 0.294, P = 0.003), while the insulin therapy period and the mean value of CCA-IMT showed a negative correlation (r = -0. 091, P = 0.376), but there was no significant differences (r = -0.091, P = 0.376). The IMT was 0.60 to 1.39 mm (mean 0.96 ± 0.19 mm). Conclusion: Two-dimensional high-frequency ultrasound may be used as an important means for evaluating the effect of the insulin therapy on atherosclerotic lesions in patients with type 2 diabetes. Early start of insulin therapy in patients with type 2 diabetes may have positive effect on slowing the progression of atherosclerosis.