Aim To investigate the effect of baseline peripheral blood circulating monocyte (MO) level on long-term mortality risk after percutaneous coronary intervention (PCI) in patients with coronary heart disease (CHD). Methods 6 045 patients with CHD treated by PCI were analyzed retrospectively. According to the level of peripheral blood circulating monocyte at baseline, the patients were divided into three groups and followed up:Ⅰ group:MO＜0.40×10⁹ L－1 (n＝1 943); Ⅱ group:0.40×10⁹ L－1≤MO≤0.56×10⁹ L－1 (n＝2 072); Ⅲ group:MO＞0.56×10⁹ L－1 (n＝2 030). The end points of follow-up included all-cause mortality (ACM), cardiac mortality (CM), major adverse cardiovascular event (MACE) and major adverse cardiac and cerebrovascular event (MACCE). The mean follow-up time was (35.9±22.6) months. Results 309 patients developed ACM, including 73 cases (3.8%) in Ⅰ group, 98 cases (4.7%) in Ⅱ group, and 138 cases (6.8%) in Ⅲ group; 251 patients developed CM, including 58 cases (3.0%) in Ⅰ group, 80 cases (3.9%) in Ⅱ group and 113 cases (5.6%) in Ⅲ group; 785 patients developed MACE, including 226 cases (11.6%) in Ⅰ group, 248 cases (12.0%) in Ⅱ group and 311 cases (15.3%) in Ⅲ group; 862 patients developed MACCE, including 250 cases (12.9%) in Ⅰ group, 269 cases (13.0%) in Ⅱ group and 343 cases (16.9%) in Ⅲ group. There were significant differences in ACM, CM, MACE and MACCE among the three groups (P≤0.001). Kaplan-Meier curve analysis of ACM and CM in the three groups showed that the prognosis of patients was worse with the increase of baseline peripheral blood circulating monocyte level (P＜0.05). COX regression analysis showed that the increase of baseline peripheral blood circulating monocyte level was independently correlated to the occurrence of ACM (Ⅲ group vs Ⅰ group, HR=1.8,5%CI:1.056-1.905, P＝0.020) and CM (Ⅲ group vs Ⅰ group, HR=1.5,5%CI:1.023-1.983, P＝0.036). Conclusion High levels of baseline peripheral blood circulating monocyte level are an independent predictor of long-term mortality risk in CHD patients after PCI.