Abstract: The present invention provides a flexible extension conduit, in which a basic unit includes a joint base, two joints, two ball valves, a sliding pipe, two dirt covers, a flat pipe, two damping collars and two embedded retainers, and so on. Therein the embedded retainer is placed in the caulking groove of the ball valve so that the caulking groove of the embedded retainer catches the catching rim in the caulking groove of the ball valve. The sliding pipe is put in the ball valve and welded a thrust collar at the smaller end to limit the sliding range of the sliding pipe in the ball valve, and the combined ball valve is located in the spherical bearing consisting of the joint base and the joint. When the earth crust moves or the temperature gets a great changing, the dirt cover can prevent the sand and the soil from seeping in, and the conduit can change the length and bend an angle in each section.