Abstract: Mainly based on "Psychological Decompensation Hypothesis" and Conservation of Resources Theory, this study investigated the development and change of middle school students' hope and smartphone addiction and their mutual prediction relationship. Hope Scale and Smartphone Addiction Scale were used to conduct a 17-month two-stage longitudinal follow-up survey on 373 middle school students. The results showed that: (1) The analysis of variance showed that the main effects of time about hope and smartphone addiction were both significant for middle school students. the specific performance was that the pre-test hope was higher than the post-test one; while the pre-test smartphone addiction level was lower than the post-test one; (2) Correlation analysis showed that there was a significant negative correlation between hope and smartphone addiction about middle school students; (3) Cross-lagged analysis showed that the hope of the pre-test can significantly predict smartphone addiction of the post-test. The smartphone addiction of the pre-test can also significantly predict the hope of post-testing. According to this study, Middle school students' hope and smartphone addiction both have developmental changes within a certain period of time. Hope and smartphone addiction can be mutually predictable and interact as both cause and effect. The results not only found that smartphone addiction will accelerate the loss of the psychological resource of hope for middle school students, but also help middle school students to give full play to the positive role of hope and reduce the risk of smartphone addiction.