The utility model discloses a tunnel center drainage ditch construction formwork. The formwork comprises a first formwork body and a second formwork body, second I-shaped steel is arranged between thefirst formwork body and the second formwork body, supporting rods are arranged at the upper end of the first formwork body and the upper end of the second I-shaped steel at equal intervals, the second formwork body is connected with the middle of the second I-shaped steel through a first connecting rod, and the second formwork body is connected with the bottom end of the second I-shaped steel through a second connecting rod. The formwork has the advantages of being light, simple in formwork supporting, more convenient to use, safer, more complete and more attractive, short in construction period, convenient to operate, capable of saving materials, capable of being recycled, high in construction risk resistance, capable of guaranteeing quality easily, economical and reasonable in construction investment, more attractive in ditch pouring and the like.