Aim Take coronary heart disease patient's peripheral blood mononuclear cells (PBMC)as the study object, observing the effect of niacin to the expression of cyclic adenosine monophotosphate (cAMP)and adenosine triphosphate binding cassette transporter A1 (ABCA1) in PBMC which incubated in vitro, analysing the correlation of niacin adjusts the expression of ABCA1 and cAMP/ protein kinase A (PKA) pathway. Methods To detect the expression of ABCA1 mRNA and protein by reverse trancriptase-polymerase chain reaction (RT-PCR) and western blot, to determine the level of cAMP in PBMC by low pH EIA kit. Analysing the expression of ABCA1 change and cAMP level change, discuss the correlation on the expression of ABCA1 and cAMP in PBMC by the role of niacin. Results (1)Each group of the expression of ABCA1 and the cAMP level changes in PBMC in 3 h and 48 h does not have the obvious difference (p<0.05). (2)The expression of ABCA1 of coronary heart disease high blood fats patient in PBMC compares the normal person obviously to reduce (p<0.05), but in the normal blood fats group the expression of ABCA1 in PBMC compares the normal person not to have the obvious change (p<0.05). (3)The niacin alone affects obviously increase in coronary heart disease person uninuclear cell the ABCA1 expression (p<0.05), at the same time makes the cAMP content in the PBMC to increase (p<0.05). (4)PKA inhibitor Ro 31-8220 alone affects can obviously reduce in coronary disease person he expression of ABCA1 in PBMCs (p<0.05),at the same time causes the cAMP content in PBMCs to reduce (p<0.05). (5)In the niacin +PKA inhibitor group were preincubated for 30 minutes in the presence of PKA inhibitor Ro 31-8220 (900 nmol/L), before niacin (1 000μmol/L)was added. then the niacin increases the expression of ABCA1 and the cAMP content in PBMCs was suppressed completely (p<0.05). Conclusion According to the result analysis of the experiment, the effect that niacin affect the expression of ABCA1 through the pathway of cAMP/ PKA, and there is an explicit correlation that niacin increase the expression of ABCA1 in PBMCs with the pathway of cAMP/PKA.