There are somewhat inseparable relationships existing between life stress and mental health. The adolescents from single-parent families not only have to face sudden physical and mental changes during. their adolescence but also have to face the influences of a incomplete family structure. Hence, the stress they feel is greater than that which the adolescents from intact families feel. Welfare delivery services have been a popular topic in recent years, but it has also been an issue seldom discussed in the past. Therefore, this research took welfare delivery services as an intermediary variable to understand the role it plays to intervene between life stress and mental health which adolescents from single-parent families feel. This research adapted a purposive sampling method, selecting 636 students who came from single-parent families out of 22 junior high schools in Taipei Municipal City, then sifted 242 adolescents from single-parent families who matched the requirements of this research as formal samples. Through proper statistical procedures, the results and findings are as follows:1.There are significant differences existing among adolescents from single-parent families upon life stress regarding gender, socio-economic status, and origins formed as the single-parent families. 2.There are significant differences existing among adolescents from single-parent families upon the degree of the intervention of welfare delivery services regarding gender, grade level, socio-economic status, and origins formed as the single-parent families. 3.There are significant differences existing among adolescents from single-parent families upon mental health regarding their gender, and grade level. 4.There is a negative relationship existing between life stress and mental health. There is a positive relationship between the level of the intervention of welfare delivery services and mental health. 5.Individual psychological stress, self interpersonal evaluation, schoolwork stress, and interpersonal relationship stress can predict 50.39% variance overall mental health. 6.The intervention of welfare delivery services can moderate the relationship between life stress and mental health. 7.Whether the level of life stress will effect mental health or not depends on the degree of the intervention of welfare delivery services.