Mobile phone dependence refers to the excessive use of mobile phones by individuals, which may cause problems in study, work and life. We compared differences in mobile phone dependence among Chinese and Czech university students, and explore the relationship between mobile phone dependence and academic achievement among them in this paper. The subjects of this study included 358 Chinese university students and 282 Czech university students who were recruited during March to April 2022. We collected data through online questionnaires, using the Short Version of the Smartphone Dependence Scale (SAS-SV) to assess the level of students' mobile phone dependence and the Academic Achievement Questionnaire (AAQ) to assess the level of students' academic achievement. The results show that for the level of mobile phone dependence are negatively correlated with the scores of various dimensions of academic achievement and the total score of academic achievement, among them, Chinese students have more significant effect in the relationship between mobile phone dependence and study performance; moreover, the correlations between the three sub-factors of academic achievement in Chinese students were stronger. It can be concluded that mobile phone dependence may lead to lower study performance, more difficulty in handling study demands, and lower social adaptation, or lower academic achievement may also lead to more severe mobile phone dependence.