Aim To measure the activity of nuclear factor-κB (NF-κB) of the peripheral blood mononucleus cells (PBMC) of patient which had acute coronary syndrome (ACS) or stable angina or hypertension, study its relationship with C-reactive protein (CRP), plaque stability and determine its value in the diagnosis of ACS. Methods We compared the results of the activity of nuclear factor-κB and levels of CRP in ACS aged 48-80 years with that of the stable angina (SA) or hypertension as controls. Results OD of NF-κB p50 of PBMC and CRP in ACS group on admission was significantly higher than that in SA group and hypertension group (p<0.01), OD of NF-κB p50 of PBMC and CRP in AMI group on admission was significantly higher than that in UA group (p<0.05). OD of NF-κB p50 of PBMC and CRP in SA group had no difference from that in hypertension group. After two weeks, OD of NF-κB p50 of PBMC in ACS group was significantly decreased compared with that on admission (p<0.01). There was no difference between SA group and hypertension group. There was a positive correlation between OD of NF-κB p50 of PBMC and blood glucose level (r=0.512, p<0.01) in ACS group. OD of NF-κB p50 of PBMC also had a positive correlation with serum CRP level(r=0.771, p<0.01). Conclusions The activation of NF-κB in peripheral blood mononucleus cells may be a predictor of the coronary plaque instability and disruption, and it might be helpful in the diagnosis of ACS.