Objective: To explore the optimal 24-hour movement behavior (24 h MB) time compositions and equivalent time-reallocation schemes associated with health-related quality of life (HRQoL) among junior high school students, thereby providing empirical evidence for scientifically guiding adolescents in the rational allocation of 24 h MB. Methods: A total of 513 junior high school students were collected from 4 junior high schools in Chengdu by the convenient sampling combined with cluster random sampling method, from September 2025 to April 2026. The 24 h MB was measured using accelerometers combined with sleep logs, and HRQoL was evaluated using the Chinese version of the Child Health Utility 9D. Compositional multiple linear regression, optimal time-zone analysis, time-substitution models, and the equivalent effect analysis were employed to analyze the associations between 24 h MB and HRQoL among junior high school students. Results: The overall 24 h MB of junior high school students was significantly associated with HRQoL ( F =7.41, P <0.01). The 24 h MB time composition associated with optimal HRQoL was as follows:low intensity physical activity (LPA) of 248 (160-350) min, moderate to vigorous physical activity (MVPA) of 84 (70-90) min, sedentary behavior (SB) of 550 (440-670) min, and sleep (SLP) of 558 (500-620) min. When MVPA or SLP was increased proportionally by 10% of duration, as well as a corresponding proportional decrease by 10% of duration in SB, and when SB was isotemporally substituted with the remaining MB (15 min of LPA, MVPA or SLP), the predicted HRQoL scores increased respectively 0.003, 0.019, 0.040, 0.008, 0.017, 0.008 (all P <0.05). The equivalent effect analysis indicated that equivalent changes in predicting HRQoL scores could be achieved through different 24 h MB time allocation schemes. To achieve a 0.1 unit ( s ) improvement in predicted HRQoL scores, it would require a proportional increase of 22.5 min of MVPA or 48.3 min of SLP, a proportional decrease of 31.1 min of SB, or the isotemporal substitution of SB with 35.0 min of LPA, 15.9 min of MVPA, or 32.7 min of SLP (all P <0.05). Conclusions The 24 h MB of junior high school students is associated with HRQoL. The temporal composition of 24 h MB associated with high HRQoL could serve as an empirical reference for daily behavior time allocation.