The COVID-19 pandemic has popularized online learning as a mode of teaching and learning in universities, thereby exacerbating college students' stress levels in multiple ways. To enhance the quality of college student training, it is crucial to investigate the impact of perceived stress on their online self-directed learning. Using questionnaire data from 969 college students across China, this study performed an empirical analysis of the influence of perceived stress on their online self-directed learning, while also exploring the mediating role of phone dependence and the moderating role of self-management ability. The findings indicate that, firstly, perceived stress has a significant and positive effect on college students' online self-directed learning. Secondly, phone dependence masks the positive impact of perceived stress on students' self-directed learning, thereby weakening the effects of employment and learning stress on their online self-directed learning. Thirdly, self-management ability positively moderates the relationship between employment, social, interpersonal, and learning stress and college students' online self-directed learning. Fourthly, rural college students' online self-directed learning is more susceptible to employment, social, and interpersonal stress; vocational college students' self-directed learning is more influenced by employment, social, and learning stress; and students in the "Double First-Class" initiative universities are more likely to develop phone dependence. Therefore, this paper asserts that using stress reasonably, controlling stress appropriately, channeling stress properly, and enhancing self-management abilities can aid college students in learning autonomous online.