Abstract: A convertible suspension mounting system for ceiling fans having a disk-shaped fixing support for being secured on the ceiling surface, a housing body of a bowl shape connected to the fixing support, a connecting device flexibly coupled with the housing body at one end and screw-connected to a pipe fitting of a ceiling fan structure. The connecting device includes a tubular connecting member with screw threads and a through hole respectively formed at each end, a circular coupling member screw-connected to the connecting member at the upper portion, and an axially flexible pipe sleeve fastened between the circular coupling member and the bottom side of the housing body with the upper portion of the connecting member flexibly received therein, so that the connecting member is provided with an axial deviation for adapting to various ceiling surface conditions, and the suspension system can be conveniently converted into a direct coupling system without the connecting device.