Objective To understand the knowledge of and motivation for participation in mutual support groups for the aged among community-dwelling young-old adults, so as to provide reference for improving their participation in mutual support for the aged. Methods According to the principle of data saturation, 15 community-dwelling young-old aults were selected using purposive sampling for semi-structured interviews, then content analysis was utilized to collate and analyze the interview data. Results Two themes were extracted: knowledge of and motivation for participation in mutual support groups for the aged (mutual benefits, expression of values, experience learning and altruism). Conclusion Community-dwelling young-old adults have a high acceptance of mutual support for the aged in the community, while their knowledge level is low. Their motivation to participate in mutual support groups for the aged in the community is clear, and it is specific.Community should ramp up propaganda and emphasize the role of "intrinsic reward", so as to improve the development of mutual support for the aged in community.