Objective To evaluate the performance of serum small dense low-density lipoprotein cholesterol(sdLDL-C) kit using enzymic method and investigate the clinical value in coronary heart disease (CHD).Methods According to the standard of Clinical and Laboratory Standards Institute (CLSI),evaluae the precision,linearity ranges,reportable range and accuracy of sdLDL-C kit.The 683 patients with coronary heart disease (CHD,423 men and 260 women,age 35-79 years) who were diagnosed at the people's hospital of Peking university from October 2015 to October 2016 were divided into two groups.The treated group include 571 patients(CHD1,342 men and 229 women,age 40-79 years) which taking lipidlowering drugs and the other include 112 cases (CHD2,81 men and 31 women,age 35-70 years)without Lipid-lowing treatment.Besides,the Control group contains 472 healthy persons (274 men and 198 women,age 41-75 years),were collected from the people's hospital of Peking university between April and August 2016.The liver function,renal function,blood glucose and blood lipid in CHD group(CHD1,CHD2) and healthy control group were detected.The new enzyme assay kit was used for the determination of sdLDL-C.The data of normal distribution were compared by independent t test between the two groups.The Mann-Whitney U nonparametric test was used for comparison between two groups.Results The precision of sdLDL-C kit examination was in compliance with manufacturer'statement.The linearity was good in 0.11-2.42 mmol/L(Y =1.008 9X + 0.024 8,R2 =0.998 2),the scope of the report is 0.11-4.84 mmol/L.The level of sdLDL-C in CHD group was significantly higher than that in healthy control group,it has a statistical significance[0.824 (0.443) mmol/L,0.609 (0.361) mmol/L;Z =-5.603,P ＜ 0.001].The level of sdLDL-C in (CHD 1) was lower than (CHD 2) [0.761 (0.479) mmol/L,0.888(0.426) mmol/L;Z=-2.304,P＜ 0.021].After additional adjustment for various tradition cardiovascular risk factor,including ages,sex,CHO,TG,Hs-CRP,Lp(a),and GLU,the highest quartile of sdLDL-C comparison to the bottom quartile,the OR was 3.02,(95％ CI,1.15-9.05) for CHD.Conclusions Experiment data demonstrated that sdLDL-C kit using enzymic method has good performance in the precision,linearity ranges,reportable range and accuracy,sdLDL-C serum level was significantly higher in CHD group.