Objective: To explore the completion status and related factors of preventive anti tuberculosis therapy among close contacts of pulmonary tuberculosis cases in schools across Guizhou Province, so as to provide scientific evidence for optimizing preventive treatment strategies and raising the treatment completion rate among student close contacts. Methods: Demographic, epidemiological and preventive treatment related data were extracted from the Guizhou Disease Prevention and Control Cloud Platform-School Tuberculosis Management System. Totally 3 044 student subjects with latent tuberculosis infection (LTBI) who received the 3HR regimen and had final treatment outcomes between January 1, 2023 and December 31, 2025 were enrolled in the study. The χ 2 test, Mann Whitney U- test and binary Logistic regression model were adopted to analyze factors associated with the completion of preventive treatment among the student LTBI population. Results: The overall completion rate of preventive treatment was 74.24%. The prevention treatment completion rate declined with prolonged medication duration( χ 2 trend =252.09, P <0.01). Binary Logistic regression analysis indicated that students from private schools had higher odds of incomplete treatment compared with those from public schools ( OR =1.32, P <0.05). Compared with college students, students in primary school and below, junior high school, senior high school, secondary vocational school exhibited lower odds of incomplete treatment ( OR =0.35, 0.31, 0.59, 0.17,all P <0.05). Compared with contacts exposed in dormitories, classroom exposed and same floor or others exposed contacts showed higher odds of incomplete treatment ( OR =4.28, 8.59, both P <0.05). Participants with an interval exceeding 2 weeks from screening to treatment initiation were more likely to complete preventive treatment ( OR =0.80, P <0.05). Conclusions The overall completion rate of preventive treatment remains unsatisfactory among students with LTBI in Guizhou Province. Multiple interventions are recommended to improve treatment adherence and completion rates in the population, including implementing diversified medication supervision measures, strengthening public health management and supervision for private schools, establishing efficient referral and management mechanisms to enhance students treatment completion.