The invention relates to a photoelectric composite connector assembly, and a plug and an adapter socket thereof. Optical fiber pins in the plug are sleeved with fitting contact members, thus the distance between the optical fiber pins and the fitting contact members is reduced, the space occupied by the optical fiber pins and the fitting contact members in the radial direction of the plug is reduced, and the problem of large size of the connector assembly caused by the spaced arrangement of optical fiber ferrules and electrical ferrules of an existing photoelectric composite connector assemblyin the radial direction is solved; meanwhile, the space occupied by fit pin sleeves and an adaptor contact member of the adaptor socket in the radial direction of the adapter socket is reduced correspondingly, and the problem of large size of the connector assembly caused by the spaced arrangement of optical fiber ferrules and electrical ferrules of the existing photoelectric composite connectorassembly in the radial direction is solved.