The invention relates to a combined lower crossbeam of a large free forging hydraulic machine, which belongs to field of hydraulic machine technology. The combined lower crossbeam of the large free forging hydraulic machine is in a beam type structure, is characterized in that: the lower crossbeam of the hydraulic machine is in a combined structure, is formed by assembling a welding frame, meanwhile, the welding frame comprises a middle-part welding frame, middle-side part welding frames and outer-side part welding frames, wherein, the middle-part welding frame and the two middle-side part welding frames and the two outer-side part welding frames are relatively assembled together through a tension pull rod. The invention has advantages of simple structure, tightening combination, convenient using, low cost, high hydraulic pressure, large processing size, and wide range of application and the like.