The utility model relates to transmission mechanisms, in particular to an adjustable floating tensioning mechanism for a multi-axis same power source. The adjustable floating tensioning mechanism comprises an underframe and two transmission wheels fixedly mounted on the underframe through bearing pedestals, wherein a lower floating frame is mounted on the underframe in a hinging way; an upper floating frame is further arranged on the lower floating frame; one end of the upper floating frame is hinged to the lower floating frame, and the other end of the upper floating frame is supported on the lower floating frame through an adjusting rod; the power source is fixedly mounted on the upper floating frame; a source transmission wheel is fixedly mounted on the power source, and is respectively connected with the two transmission wheels of the underframe through belts or chains. According to the utility model, adjustment is realized through an adjusting screw rod between the two floating frames in floating, and floating of the axis of the power source is realized through adjusting the interval between the two floating frames, so that simultaneous multi-wheel tensioning can be realized through adjusting the positions of the floating frames; the structure is simple, and the production-manufacturing and maintenance costs are low.