The utility model discloses a sand box preformer, including frame, two sets hydraulic jack (1), bearing pressure beam (2) and sand box (3), the frame include entablature (4), bottom end rail (5) and two stand (6), both ends about two stand (6) about entablature (4) are fixed in respectively with bottom end rail (5) constitute square steel structural framework, bearing pressure beam (2) are locatedthe frame in the middle part, upper surface two set fixed hydraulic jack (1) side by side of frame inherent bottom end rail (5), lower surface that the ejector pin tip of hydraulic jack (1) passes through ball joint seat (9) to be fixed in bearing pressure beam (2), last surface mounting sand box (3) of bearing pressure beam (2), the lower surface of frame inherent entablature (4) be equipped with sand box (3) bearing area. Can the accurate compression load in advance who guarantees the sand box to effective construction safety that ensures the bridge of turning.