BACHGROUND: This study aimed to explore the association between lipoprotein(a) (Lp(a)) and lymphocyte count in patients with unstable angina (UA), non-ST-segment elevation acute patients with unstable angina (UA), non-ST-segment elevation acute myocardial infarction (NSTEMI), and ST-segment elevation acute myocardial infarction (STEMI). METHODS: A total of 1888 patients, including 1272 patients with UA, 266 patients with NSTEMI, and 350 patients with STEMI at the Cardiovascular Center of Beijing Tongren Hospital were included in the study from February 2022 to April 2023. Data were gathered from the medical record system and included age; sex; smoking status; drinking history; medical history of hypertension, diabetes mellitus, and hyperlipidemia; anticoagulation, antiplatelet, lipid-lowering, blood pressurelowering, and glucose-lowering discharge medication; and clinical parameters (lymphocyte counts, neutrophil counts, erythrocyte counts, hemoglobin, uric acid, albumin, lactic dehydrogenase [LDH], Lp(a), total cholesterol [TC], triglyceride, high-density lipoprotein cholesterol [HDL-C], low-density lipoprotein cholesterol [LDL-C], glycosylated hemoglobin [Hb1Ac], fibrinogen, antithrombin III, and free thyroxine [FT4]). The nonparametric Wilcoxon test was used for the statistical analysis of variables across groups. Categorical variables were presented as percentages. Spearman correlation analysis was performed to examine the association between Lp(a) and other variables. RESULTS: In the UA group, the Lp(a) level was significantly positively correlated with LDL-C, HDL-C, TC, LDH, and fibrinogen and negatively correlated with TG, albumin, Hb1Ac, uric acid, lymphocyte count, erythrocyte count, and hemoglobin. In the NSTEMI group, the level of Lp(a) was significantly positively correlated with LDL-C, TC, fibrinogen, and antithrombin III and negatively correlated with lymphocyte count (P < 0.05). In the STEMI group, the level of Lp(a) was significantly positively correlated with LDL-C, TC, neutrophil count, fibrinogen, and LDH and negatively correlated with lymphocyte count, albumin, and FT4 (P < 0.05). CONCLUSIONS: The level of Lp(a) was significantly negatively correlated with lymphocyte counts in patients with UA, NSTEMI and STEMI. The study indicated that the main role of Lp(a) in different stages of CHD may vary. Lp(a) has an enhancing effect on thrombosis in different stages of CHD and both pro-thrombotic and pro-inflammatory effects in acute ST-segment myocardial infarction. This study provides a theoretical basis for the reduction of Lp(a) levels in patients with CHD.