The utility model discloses a three-main-truss bolting and welding combined cable-stayed bridge steel beam whole section total splicing truss width control device. Wherein the fixed end module is welded and fixed with a welded whole section, and the sliding end module is welded and fixed with a to-be-welded whole section. The fixed end module comprises a fixed panel; the sliding end module comprises a sliding panel; six sliding locking holes are formed in the sliding panel; four fixed locking holes and two sliding guide holes are formed in the fixed panel, the four fixed locking holes are connected with the four sliding locking holes in the sliding panel through locking hole limiting punching nails, and the two sliding guide holes are connected with the two sliding locking holes in the sliding panel through sliding groove guide punching nails. According to the device, the welding shrinkage allowance between the truss pieces is reserved when the whole section is spliced and positioned,the development of welding shrinkage deformation is not limited, and the residual stress in the welded structure is reduced as much as possible.