A fast-connecting joint for corrugated pipes includes a main body and an engaging member. The main body has a through hole for liquid to flow through, and an inner recessed annular wall provided with an annular slope close to one end of the main body. The engaging member possesses an outer annular wall, and plural flexible curved petals extending outward around one end of the outer annular wall and respectively having a projection on their outer surface. In assembly, the engaging member is inserted in the through hole of the main body, with the projections of the engaging member correspondingly fitted against the inner recessed annular wall. In use, a corrugated pipe can be quickly fastened with the fast-connecting joint tightly when it is inserted into the engaging member to keep its annular groove blocked by the curved petals.