The invention provides a stair formwork. The stair formwork comprises an oblique plate, a serration plate, multiple stepping profiles and seal plate assemblies, and the oblique plate is a rectangular plate, the serration plate is located on the lower portion of the oblique plate and fixedly connected with the oblique plate; the steeping profiles are spliced one by one to form trapezoidal structures, and the ends, on the same side, of the steeping profiles are all fixedly connected with the serration plate; each stepping profile comprises a rectangular first stepping plate, a rectangular second stepping plate perpendicularly extending from one end of the first steeping plate and a rectangular third steeping plate perpendicularly extending from one end, far away from the first stepping plate, of the second steeping plate; each seal plate assembly comprises a rectangular first seal plate and a rectangular second seal plate perpendicular to the first seal plate, and each first seal plate is fixedly connected with the corresponding second seal plate. Compared with the prior art, the stair formwork has the advantages that the integrity and strength are better, production and manufacture are convenient, the project construction efficiency is improved, and the cost is saved.