The invention relates to the engineering technique for protecting a river dyke, in particular to a method for constructing a relief well, comprising the steps of: hole creating, hole cleaning, borepipe making and hoisting, filter material making and filling, hole flushing, pumping test and well top processing, etc. The method is characterized in that: in the hole creating step, a direct soil-borrowing type drilling machine is used to create holes, and created holes are protected by high polymer composite slurry; in the hole clean step, the high polymer composite slurry is directly used to clean holes, and the hole clean step includes a cyclic process of the recovery, the purification, the storage and the reutilization. The high polymer composite slurry is prepared by following components in portion by weight: 1000 portions of water, 70 to 130 portions of bentonite, 5 to 25 portions of polyacrylamide, 2 to 15 portions of cellulose ether, 0 to 9 portions of weight additive, 0 to 5 portions of industrial alkali and 0 to 3 portions of fluid loss additive, and the mixture is stirred into slurry by a swirling flow type pulping machine. The method has the advantages of easy and quick operation, high production efficiency, good product quality and long service life; moreover, in the process of construction, the method has the advantages of energy and water conservation, low cost, low noise and no pollution.