In order to understand the truants’ self-concept influencing and changing situations after finishing experiencing the institutional treatment, returning to school, and resuming interrupted studies, the research adopted qualitative in-depth interview and purposeful sampling to seek for the interview objects that tallied with the research conditions until the samples were saturated. I interviewed seven truant juvenile status offenders in total, and utilized the software: WinMAX system to assist to do the encoding of original data. The research findings are as follows: 1. The institutional treatment made the truant status offenders have a change on self-concept after resuming interrupted studies, and the impact factors consisted of twenty-nine self-cognition factors, of which the content included the influence of the course of treatment, “the motive power with the feeling of shame” caused by the function of institutional treatment, and the truants’ change on self-concept of “re-molding of self-relationship,” and “re-molding of the relationship between people and oneself.” 2. The appearance sequence of self-concept changing factors were “the period of knowing the shame,” “the period of gradual change,” and “the stereotyping period.” 3. After these juveniles returned to school and resumed interrupted studies, it was not that the situation of cutting class never occurred again, but at least, they could keep the condition of not being reported as dropouts anymore; the ones that chose to return to school and resume their interrupted studies voluntarily had a better and steadier condition of recovery of schooling than those who did it passively; the main reason that the juveniles’ condition of running away from school could be decreased was because they did not want to be sent to any institution for detention and settlement anymore. 4. After the institutional treatment ended, the truants adapted themselves well to the family, the school, and the society, and their relationship with others developed toward a positive direction. 5. The original relationship between the teacher and the student affected the teacher’s label effect for the truant; the labeling problem among classmates did not occur often; the labeling phenomenon did not appear among social peers, and the association among peers or the situation of knowing new peers was not influenced. 6. To evaluate from the whole, institutional treatment had an intimidation effect on the truants after resuming interrupted studies, and it could achieve the result as in “reintegrative shaming,” improve the juveniles’ condition of running away from school, and make their self-concept change toward a positive direction. Therefore, for the frequent truants, to hand over the cases to the court according to the Handling of Juvenile Delinquencies Law is not inappropriate. Finally, the research made suggestions for the police system, the correction institution, the school system, and the probation system, expecting to arouse the relevant personnel’s paying attention to the prevention and handling of truant status offender events, as well as their efforts.