Plastic formwork for building slab

The invention provides a plastic formwork for a building slab. The plastic formwork comprises a front plate and a frame, wherein the frame is vertical to the surface of the front plate; a plurality of connecting holes for connecting with other formworks are formed in the frame; a ribbed plate vertical to the surface of the front plate is arranged on the back of the front plate; the ribbed plate comprises a main ribbed plate and a secondary ribbed plate; the back of the front plate is divided into a plurality of rectangular partitioning areas, which are arranged longitudinally and transversely, by the main ribbed plate; the back of the front plate in the rectangular partitioning areas is partitioned into a plurality of longitudinal and transverse square blocks by the secondary ribbed plate in the rectangular partitioning area; plug-in type protective corners are respectively installed at four corners of the front plate. The plastic formwork overcomes the disadvantage that the whole plastic formwork is scraped because of the damage of the corners; the breaking rate of the plastic formwork for the slab is reduced; advantages of high-molecular material can be utilized and disadvantages are overcome; a plate design effectively matches with a support and reinforcing system, thus a scientific and effective formwork engineering system is finished.