Objective To observe the serum level of non-high density lipoprotein cholesterol(non-HDLC),and to evaluate the relationship between non-HDLC and atherosclerosis in Hangzhou occupational population.Methods 11668 people(7369 males,4299 females) who took physical examination in our hospital during 2006.1-2007.6 were detected the fast serum levels of total cholesterol(TC),triglyceride(TG),high density lipoprotein cholesterol(HDL-C) and low density lipoprotein cholesterol(LDL-C) according to standard operating procedure.And then non-HDLC and atherogenic index of plasma(AIP) were calculated according to the formulae non-HDL-C =TC-HD-C and AIP=log(TG/HDL-C).Statistical analysis was performed to evaluate the correlation between non-HDLC and atherosclerosis.Results There was a significant difference of LDL-C between by direct assay and by Friedewald formula calculation(P<0.001).When TG<4.5mmol/L and TG without grouping,LDL-C calculated by Friedewald formula was higher than that by direct assay.When TG≧4.5mmol/L,LDL-C calculated by Friedewald formula was obviously lower than that by direct assay.Non-HDLC was more closely related to AIP than LDLC as comparing TC and TG on different levels.Conclusions Non-HDLC was more closely related to AIP,and it could be used to judge the chanciness of atherosclerosis.Therefore,we suggest that the value of non-HDLC and AIP should be combined on analyzing routine blood fat to elevate the accuracy of artherosclerosis evaluation and non-HDLC as the second target in blood fat treatment.