The utility model provides an expansion instrument of formula rail nondestructive reinforcing device is pressed from both sides to elasticity relates to the railway track damage and consolidates technical field, has solved the current technical problem that expansion tool function is single. This expansion instrument includes tensile indexing mechanism and actuating mechanism, wherein: elasticityis pressed from both sides formula rail nondestructive reinforcing device and is included that elasticity is pressed from both sides and two splint of symmetry, two splint grasp the abdominal both sides of rail, tensile indexing mechanism with actuating mechanism is connected, actuating mechanism can drive tensile indexing mechanism will elasticity is pressed from both sides will be at the state of opening from free state drawing to the state of opening the elasticity clamp rotates to the centre gripping and locks two the position of splint. The utility model discloses can press from both sides elasticity from free state drawing to the state of opening and can will rotate to the centre gripping at the elasticity clamp of the state of opening and lock two the position of splint has increased the function of expanding the instrument.