随着智能手机成为人们日常生活中的必需品，人们每天使用手机的时间变得越来越多。手机在为人们带来便利的同时，也会对人们产生不利的影响。尚在身心发展关键时期的中学生，非常容易产生过度的手机使用即问题性手机使用。以往的研究发现，自尊能显著预测问题性手机使用，但这两者之间的作用机制尚不明确。同时，低自尊也是人们产生社交焦虑等负性情绪的重要原因。存在社交焦虑的人在网络、社交媒体等工具的使用上，更容易出现逃避动机。逃避动机也被证明，能显著预测问题性手机使用。本研究假设，社交焦虑和逃避动机可能是自尊和问题性手机使用这两者之间的中介，来进行进一步的探讨。 本研究通过问卷调查法，在北京市某中学开展研究，共有448名被试参与。本研究探讨中学生自尊、社交焦虑、逃避动机、问题性手机使用四者之间的关系，得出以下结论： (1)被试的自尊和逃避动机均存在性别差异； (2)社交焦虑、逃避动机、问题性手机使用均在不同年级上存在显著差异； (3)社交焦虑和自尊呈显著负相关；逃避动机与自尊呈显著负相关，与社交焦虑呈显著正相关；问题性手机使用与自尊呈显著负相关，与社交焦虑呈显著正相关，与逃避动机呈显著正相关； (4)社交焦虑和逃避动机在自尊和问题性手机使用之间起完全链式中介作用。共有三条间接效应的路径显著。分别为：①间接效应1：自尊→社交焦虑→问题性手机使用；②间接效应2：自尊→逃避动机→问题性手机使用；③间接效应3：自尊→社交焦虑→逃避动机→问题性手机使用。 综上，本研究的结果表明：低自尊的个体更容易产生社交焦虑，而社交焦虑导致的逃避动机，会进一步引发问题性手机使用。因此，为了减少中学生的问题性手机使用，应该从其作用机制入手，对学生进行有针对性的引导和干预工作。例如，家长和教师要注意培养、保护学生的自尊；采取多种方式，降低学生的社交焦虑，帮助学生建立良好的人际关系，从而避免学生因在现实中遇到困难而产生逃避动机，引发问题性手机使用。

As smartphone has become a daily necessity in people’s life, the time people spending in phone use was longer than before. On the one hand, smartphone made our daily life more convenient. On the other hand, it also had shortcomings. The middle school students, who are still in the key period of physical and mental developing, are very easily to be trapped by smartphone and suffered problematic mobile phone use. Previous studies have found that self-esteem can significantly predict the use of problematic mobile phone use. However, the mechanism between the two is not clearly proved. Meanwhile, it is also well documented that low self-esteem will lead to negative emotions such as social anxiety. Those who have social anxiety are more tend to use techniques such as Internet and phones for escapism motivation. And escapism motivation will cause problematic mobile phone use. This study hypothesized that social anxiety and escape motivation might be the mediators between self-esteem and problematic mobile phone use. In the present study,448 middle school students in Beijing was recruited for the study. All the participants have finished the questionnaire to report their situation for self-esteem, social anxiety, escapism motivation and problematic mobile phone use. The findings are as follows: (1) There were significant gender differences in self-esteem, boys scored higher than girls; there were significant gender differences in escape motivation, boys scored lower than girls. (2) There were significant differences in social anxiety. there were significant differences in escapism motivation between different grade. There were significant differences in problematic mobile phone use between different grade. (3) There was a significant negative correlation between social anxiety and self-esteem; escapism motivation is significant negative correlated with self-esteem and positive correlated with social anxiety; problematic mobile phone use is significant negative correlated with self-esteem, positive correlated with social anxiety and positive correlated with escapism motivation. (4) Social anxiety and escapism motivation have a sequential mediation effect between self-esteem and problematic mobile phone use. There are three indirect pathways: firstly, self-esteem could affect problematic mobile phone use through the mediation role of social anxiety; secondly, self-esteem could affect problematic mobile phone use through the mediation role of escapism motivation; thirdly, self -esteem could affect problematic mobile phone use through the sequential mediation role by social anxiety and escapism motivation. To conclude, these findings show those who have low self-esteem is more easily to have social anxiety, which will lead to the escapism motivation and finally cause problematic mobile phone use. After understanding this mechanism, there are some key points should be well noticed when teachers and parents do intervention about students’ smartphone use.For instance, the parents and teachers should help middle school students to improve and protect their self-esteem and they should try multiple solution to help the students cope with social anxiety and build up good interpersonal relationship which could prevent their escapism motivation when they face some obstacles in the daily life and tend to phones to escape.