Abstract：The DFT-B3LYP method, with the basis set 6-31G, was employed to calculate the molecular geometries and electronic structures of 24 3-substituted sulfur-5-(2-hydroxyphenyl)-4H-1,2,4-triazole compounds. EHOMO, ELUMO, ENHOMO, ENLUMO, QC1～QC8, QN1～QN3, QO, QS, ΔE1, ΔE2, ΣQ were selected as quantum chemical descriptors (qc). The quantitative structure-activity relationships (QSAR) were established by using leaps-and-bounds regression analysis for the antibacterial activities (AJ: Am, Ae and As) of 13 compounds to Escherichia coli, Monilia albican and Staphylococcus aureus along with the qc. The correlation coefficients (R2) and the leave-one-out (LOO) cross validation Rcv2 for the Ae, Am and As models were 0.930 and 0.871; 0.926 and 0.869; 0.781 and 0.572 respectively. The QSAR models have both favorable estimation stability and good prediction capability by Aadj2, F, Rcv2, VIF, AIC, FIT tests. The results indicate that the ΔE1 and ΣQ are main factors which can affect the bioactivities of these compounds directly. The antibacterial activities of the compounds increase with the increase of the ΣQ; however the higher the ΔA1 is, the lower the AJ is. The possible mechanism has been given for the antibacterial of the triazole compounds. It is known that the suitable structural modifications of R group in triazole compounds with the strong electron- attracting one are beneficial to the antibacterial activities. According to the results (11 compounds) obtained from the structural modifications, the antibacterial activities of four modified molecules are over 100% when mass fraction is 0.01%, and it is expected to be confirmed by using biologic experiments.