The study was investigated the effects of the modified filial therapy treatment program on parental function, attachment of the adopted children, parent-child relationship, and parent stress of for the adopted children, and foster family, and their with interaction relationship and to test whether the filial therapy treatment program can improve the parental function, attachment of the adopted children,parent-child relationship, and decrease parent stress. The single-subject research design was used in this study. There were The single-subject study was conducted with four foster families involved in this study with three female and one male parents at the average age of was 45 and four the adopted children at the average age was 5. Each family took the Filial therapy program was implemented in each family for ten weeks, and their interaction would be observed and recorded for twenty weeks. The data were as analyzed with the method of visual analysis and statistical analysis. As the result of The study revealed that the data of filial therapy show from three subjects had significant intervening and maintaining efficacy on the parental function, parent-child relationship,and parent stress on three of four participants. In addition The study identified effective the therapeutic factors of the filial therapy,including conveying “be with” attitudes, allowing child to lead, following child’s lead, reflecting child’s nonverbal play behavior, reflecting child’s verbalizations, reflecting child’s feelings/wants/wishes, voicing tones matched child’s intensity/affect, responding were briefly and interactive, facial expressions matched child’s affect, used encouragement/self-esteem-building responses..