Objective To explore the situation of non-suicide self-injury （NSSI） and depression among junior high school students in Shandong Province， and analyze the intermediary role of depression between behavior inhibition/activation system （BIS/BAS） and NSSI. Methods In June 2022， a total of 2 900 students from 3 middle schools in Sishui County， Jining City， Shandong Province were recruited by cluster sampling method. Adolescent Self-Harm Behaviors Questionnaire，Behavioral Inhibition/Activation Systems Scales （BIS/ BAS scales），and Self-Rating Depression Scale （SDS） were used for investigation. Pearson correlation was used to analyze the correlation between variables. SPSS Amos 24.0 software was used to construct the structural equation model and carry out the intermediary effect test. A total of 2 900 questionnaires were distributed in this study， and 2 429 valid questionnaires were recovered， with an effective recovery rate of 83.76%. Results The annual incidence of NSSI in 2 429 junior high school students was 37.55% （912/2 429）， and the incidence of depression was 32.73% （795/2 429）. All the students were divided into NSSI group （n=912） and non-NSSI group （n=1 517） according to whether there was NSSI behavior. The score of Adolescent Self-Harm Behaviors Questionnaire in NSSI group was （33.01±21.24）. The score of BIS， BAS-Fun Seeking， and SDS in NSSI group was （11.08±2.93）， （7.15±2.58） and （53.17±10.67）， all higher than those in non-NSSI group（10.16±3.15）， （6.52±2.55） and （43.16±9.77）， respectively， and the differences were statistically significant （t=-7.312， -5.838，-23.098； P ＜ 0.001）. The score of BAS-Reward Responsiveness in NSSI group was （11.64±2.53）， lower than that in non-NSSI group （12.16±2.24）， and the difference was statistically significant （t=5.084，P＜ 0.001）. Pearson correlation analysis showed that the degree of depression of junior high school students with NSSI was positively correlated with the severity of NSSI， BIS Sensitivity and BAS-Drive Sensitivity （r=0.484， 0.184，0.128； P＜ 0.01）； BAS-Reward Responsiveness sensitivity is negatively correlated with the severity of NSSI and the degree of depression （r=-0.203，-0.239；P＜ 0.01）. Regression analysis showed that depression had a positive impact on NSSI （β=0.461，P＜ 0.001）， while behavioral activation system-reward response had a negative impact on NSSI （β=-0.093，P＜ 0.01）. Results of the structural equation model showed that depression played a completely mediating role between BIS as well as BAS-Fun Seeking and NSSI，and the estimates of complete mediating effects were 0.121 and 0.204 respectively， accounting for 86.4% and 72.7% of the total effect. Depression played a partially mediating role between BAS-Reward Responsiveness and NSSI， and the estimate of the partial mediating effect was -0.199， accounting for 58.2% of the total effect. Conclusions The incidence of adolescent NSSI is relatively high. Depression plays a complete mediating role between BIS，BASFun Seeking and NSSI，and plays a partial mediating role between BAS-Reward Responsiveness and NSSI.