This study aimed to investigate the association of high-risk culprit plaque features by optical coherence tomography (OCT) with residual SYNTAX score (rSS) and the predictive value of rSS for major adverse cardiac events (MACE) in patients with ST segment elevation myocardial infarction (STEMI). We included 274 patients and divided them into 3 groups — rSS=0 (n=72), 0<rSS≤8 (n=134), and rSS>8 (n=68). There were significant differences in plaque characteristics among three groups (plaque rupture: 44.4% versus 59.0% versus 64.7%, lowest to highest rSS, p=0.040; OCT-defined high-risk plaques: 16.7% versus 23.9% versus 35.3%, lowest to highest rSS, p=0.036; calcification: 38.9% versus 52.5% versus 61.8%, lowest to highest rSS, p=0.024). During a mean follow-up of 2.2 years, MACE occurred in 47 (17.2%) patients; rSS >8 group had higher MACE risk compared to rSS=0 (HR: 2.68, 95%CI: 1.11–6.5, P=0.029). In conclusion, culprit plaque morphology was significantly correlated with rSS, and elevated rSS was associated with higher cardiovascular risk in STEMI patients. ClinicalTrials.​gov: NCT03593928