The main purpose of this study was to investigate the relationships among the ability to be alone, loneliness, and life stress of elementary school students. The sample consisted of 396 students from sixth grade students in Taoyuan county. The data for this study was collected through questionnaire surveys. Instruments used in this study included the Ability to be Alone Scale, the Loneliness Scale, and Life Stress Scale. The results was listed as the following: (a) There were middle to low level of students’ life stress; (b) there was significant difference between family types in the “family stress” aspect of life stress; (c) there were significant correlations among the ability to be alone, loneliness, and life stress ; (d) the ability to be alone and loneliness could significantly predict life stress.