According to one embodiment a horizontal formwork system is provided that includes a pair of parallel longitudinal beams on which a safety means is coupled for protecting against falling. The safety means includes a safety structure that is located below the formwork panels. The safety structure at least partially covers a gap existing immediately after a last assembled formwork panel and displacement means for moving the safety structure in a longitudinal direction along a length of the longitudinal beams. The displacement means is configured to be operated on by an operator allow to move the safety structure to cover the gap immediately after the last assembled formwork panel. A safety method for installing formwork panels is also provide that may include the steps of assembling at least one guide to the corresponding longitudinal beam and coupling a safety structure having at least one guided element to the longitudinal beams through a guide, and sliding the safety structure along the guide to cover the gap.