Background: Current study was to evaluate association of Lipoprotein (a) [Lp(a)] and coronary artery lesion and in-hospital outcomes in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI).Methods: Baseline characteristics, characteristics of coronary artery lesion, medications use, and cardiovascular events during hospitalization were collected. Based on Lp(a) level, patients were divided into low (< 30 mg/dL) and high (≥ 30 mg/dL) groups. Results: Compared to those with low Lp(a), patients with high Lp(a) had larger numbers of coronary arteries ≥ 70% stenosis and longer coronary artery lesion (P<0.05). Patients with high Lp(a) were more likely to have left anterior descending artery lesion, pre-PCI TIMI flow grade 0 and post-PCI TIMI flow grade 2, and type C coronary lesion (P<0.05). After adjustment, high Lp(a) remained associated with higher odds of having coronary artery ≥ 70% stenosis, type C coronary lesion and pre-PCI TIME flow grade 1/0. Compared to those with low Lp(a), patients with high Lp(a) had a higher unadjusted odds of acute stent thrombosis (odds ratio [OR] 1.10 and 95% confidence interval [CI] 1.01-2.27), congestive heart failure (OR 1.24 and 95% CI 1.15-2.38) and composite in-hospital outcomes (OR 1.28 and 95% CI 1.18-2.42). After adjustment, patients with high Lp(a) remained had a higher odds of congestive heart failure (OR 1.08 and 95% CI 1.01-1.78) and composite in-hospital outcomes (OR 1.12 and 95% CI 1.04-1.81).Conclusion: High Lp(a) was associated with more severe coronary artery lesion, and higher risk of congestive heart failure and composite in-hospital outcomes.