Clear and blockage detection device for underground sewage pipeline and usage method thereof

The invention discloses a clear and blockage detection device for an underground sewage pipeline. A display control end is installed on the top of a length pole and the bottom is fixedly connected with an electromagnet, the bottom of the electromagnet is in shaft connection with a flow direction measurement blade, when the display control end controls the electromagnet to be energized, the electromagnet attracts the flow direction measurement blade, and when the display control end controls the electromagnet to be de-energized, the flow direction measurement blade is in a free state; the flowdirection measurement blade is connected with a bottom bar at the lower end through a bearing; a capacitance-grating ring is installed on the outer circumference of the bearing and is used for calculating orientation of the flow direction measurement blade and transmitting data to a compass display device of the display control end; and the length pole is connected with a flow meter in a perpendicular fastening manner, an