Aim To determine the relationship between remnant cholesterol (RC) and long-term cardiovascular risk in young patients with coronary artery disease (CAD). Methods 3 200 patients with CAD hospitalized from May 2013 to November 2015 were analyzed retrospectively. They were divided into three groups according to age:young group (＜45 years old), middle-aged group (45～70 years old) and elderly group (≥70 years old); They are divided into high group and low group according to RC levels. The incidence of major adverse cardiovascular event (MACE) was statistically analyzed. KM method was used to evaluate the survival rate without MACE event, and Cox regression was used to evaluate the predictors of clinical endpoint. The dose-response relationship between RC and MACE risk was demonstrated using a restricted cubic spline (RCS) model. Results A total of 3 112 patients were followed up (97.25%), including 160 in young group, 2 390 in middle-aged group, and 562 in elderly group. The median follow-up time was 7.36 years. Among them, 864 cases (27.8%) experienced MACE events. KM curve showed that RC was not a predictor of long-term MACE in patients with CAD of all ages (P＞0.05), nor was it a predictor of MACE in middle-aged and elderly groups (P＞0.05). KM curve and Cox regression showed that RC was an independent predictor of long-term MACE in premature CAD patients, and the risk of MACE increased by 1.07 times for every 1 mmol/L increase in RC (HR=2.7,5%CI:1.35～3.17, P＜0.01). Through calculation and verification, it was found that the optimal cutoff value of RC for predicting the occurrence of MACE in premature CAD patients was 0.94 mmol/L, and the risk of MACE in premature CAD patients with RC＞0.94 mmol/L increased by 1.98 times (HR=2.8,5%CI:1.41~6.32, P＜0.01); Conversely, the risk of MACE was reduced by 66% in premature CAD patients with RC＜0.94 mmol/L (HR=0.4,5%CI:0.16～0.71, P＜0.01). Conclusion RC is an independent predictor of long-term MACE occurrence in premature CAD patients (7.36 years). The optimal cutoff value of RC in this population is 0.94 mmol/L. Controlling RC below 0.94 mmol/L is able to reduce the risk of MACE by 66% in premature CAD patients.