Online learning is becoming more and more common, so how to maintain learners' online learning engagement is very important. This study aims to explore the impact of future self-continuity on college students' online learning engagement and its underlying mechanism of action. We utilized the Future Self-Continuity Questionnaire, the Learning Self-regulation Questionnaire, the Implicit Theories of Intelligence Scale, and the Online Learning Engagement Scale to measure the corresponding variables of a sample with 476 college students. The results revealed that future self-continuity, autonomous motivation, and implicit theories of intelligence were significant positive predictors of student's online learning engagement. The positive association between future self-continuity and student's online learning engagement was mediated by the autonomous motivation. Moreover, the mediating effect of autonomous motivation was moderated by the implicit theories of intelligence. Relation to the individual endorsing entity theorists, the mediating effect of autonomous motivation was stronger for individual holding increment theorists. Future self-continuity has an impact on college students' online learning engagement levels directly or indirectly through autonomous motivation. Attention should be paid to the cultivation training of learners' future scenario imagination and autonomous motivation to facilitate their maintenance of focused online learning engagement.