This study constructed a structural model of a causal relationship between locus of control and social support on life stress for junior high students. Structure equation modeling with the LISREL computer program was used to investigate the model proposed by the author. The participants were 557 seventh to ninth graders from junior high schools in Tainan. The instruments employed in this study included：Locus of Control Scale, Social Support Scale, and Student´s Life Stress Scale. The results of this study indicated：（a）according to other indices of overall model fit, the observed data could be interpreted by the maintained model although the former did not seem to fit the latter because of the significant of χ2 value,（b）sex had a significant direct effect on locus of control, but had no significant direct effects on social support and life stress,（c）sex had a significant indirect effect on social support and life stress,（d）grade had a significant direct effect on life stress,（e）locus of control had significant direct effects on both social support and life stress,（f）locus of control had a significant indirect effect on life stress, and（g）social support had significant direct effects on life stress. Moreover, the implications for the presented study were discussed and suggestions for school personnel and further research were also proposed.