More and more investigations and phenomena show that the group of college students are bored for a long time, and it is more common for the group of freshmen to feel boredom. Freshman year is a critical period of personal development. If freshmen cannot adjust their tendency to become boredom in a timely manner, boredom will have many adverse effects on their physical and mental development. On the one hand, bored individuals are often accompanied by the urge to escape this state, often using mobile phones to obtain new stimuli to escape the boring experience, thereby increasing the risk of college students' mobile phone dependence. In addition, individuals with high levels of boredom lack the motivation and vitality to do things, and their poor perception of time is also not conducive to individuals' effective management of time. On the other hand, many freshmen are faced with the problem of adapting to time management. They often passively carry out activities that they are not interested in to kill time, so it is difficult to experience the sense of time flowing, which makes the boredom more serious. Therefore, for college freshmen, it is worthy of our in-depth consideration to explore whether they become a high-incidence group of boredom due to" improper means to alleviate boredom" or" incompetence in time management during the transition period". At present, most studies have failed to explore the causal relationship between these key variables, and there are few longitudinal studies on these three variables to find out the causal order or mutual relationship between the variables. Therefore, this study adopts the cross-lag design to explore the development trends of freshmen' s time management disposition, boredom Proneness, mobile phone dependence and the interaction mechanism between them. The test starts after the military training is completed, and is retested after a month interval, a total of three measurements. The participants are freshmen from two undergraduate colleges in Shanxi Province. Each participant filled out the Adolescent Time Management Disposition Scale, Boredom Proneness Scale, and Mobile Phone Dependency Index Scale each time. After deleting lost participants and invalid questionnaires, a total of 425 valid questionnaires were obtained. Finally, SPSS25.0 and AMOS22.0 were used for data analysis, including repeated measurement variance analysis, correlation analysis and path analysis of cross-lag model. The results of the study found that: (1) At three time points, there is a significant negative correlation between time management disposition and boredom proneness, and boredom proneness and mobile phone dependence are significantly positively correlated; (2) The boredom proneness at T1 and T2 can positively predicts the mobile phone dependence at T2 and T3 respectively, and also can negatively predicts the time management disposition at T2 and T3 respectively; The time management disposition at T1 can negatively predicts the boredom proneness at T2, the mobile phone dependence at T2 can positively predicts the boredom proneness at T3. Therefore, the boredom proneness as a more stable antecedent variable enlightens us to pay attention to the boredom proneness of freshmen and intervene in time to avoid it causing more adverse effects. At the beginning of the semester, we should help students improve their time management disposition and avoid the deterioration of their boring proneness. To deal with students' mobile phone dependence, prevention should be the first priority, and students should develop good mobile phone habits to avoid negative effects on the boredom proneness.