Abstract: Objective To investigate the correlation between low-density lipoprotein cholesterol(LDL-C)to high-density lipoprotein cholesterol(HDL-C)(LDL-C/HDL-C)and carotid atherosclerosis(CAS)in middle-aged and elderly patients with type 2 diabetes mellitus(T2DM). Methods A total of of 220 middle-aged and elderly patients with T2DM were divided into T2DM without CAS(T2DM-NCAS )group(CIMT<1.0 mm)and T2DM with CAS(T2DM-CAS)group(CIMT≥1.0 mm)by demarcation point value of carotid intima-media thickness(CIMT)according to Color doppler ultrasound diagnosis results, with 110 cases in per group. The basic clinical data and biochemical indexes of all the subjects were collected. Spearman correlation analysis and Logistic regression analysis were used to evaluate the influence factors for the CAS in T2DM. All participants were divided into three groups according to LDL-C/HDL-C levels and prevalence rates of T2DM-CAS were compared. Results Compared with T2DM-NCAS group, the ratio of LDL-C to HDL-C was significantly increased in T2DM-CAS group(P< 0.01). T2DM-CAS was positively correlated with disease course, glycosylated hemoglobin(HbA1c), serum cystatin C(Cys C), apolipoprotein B(ApoB), total cholesterol(TC), low density lipoprotein cholesterol(LDL-C)and LDL-C/HDL-C, but was negatively with high density lipoprotein cholesterol(HDL-C)(P< 0.05 or P< 0.01). Binary Logistic - regression analysis showed that disease course, HbA1c, Cys C, and LDL-C/HDL-C were the independent risk factors for CAS in middle-aged and elderly patients with T2DM(P< 0.05 or P<0.01). The incidences of T2DM-CAS were 34.24%, 54.79%, 60.81%, respectively, in ratio of LDL-C to HDL-C<2.15, 2.15~2.65, >2.65(P<0.01). Conclusion The ratios of LDL-C to HDL-C may be better indicators for the early detection of CAS in middle-aged and elderly patients with T2DM compared with detection of LDL-C levels alone.