Objective:To explore the loneliness and perceived social support(PSS) correlation of Chinese bereaved parents of only-child(named "Shi Du Zhe" in China,refers to those couples,above 49 years old,had only one child as a result of Chinese birth control program started from 1980s,but run into unexpected bereavement and even offspring shortage after 20-30 years),and to examine potential differences in the two indicators of mental health between these parents and the lonely childless elders(named "Gu Gua Zhe",means spouseless and childless,refers in particular to those never-married,divorced or widowed,have no own or adopted child,above 60 years old and cannot support themselves in general),as both of them are two social vulnerable groups in China which have certain similarities.Methods:55 parents who had lost his/her only-child were recruited to fill in UCLA Loneliness Scale(3rd edition) and Perceived Social Support Scale on the Internet.