The invention discloses a double-layer casing sand-control well completion technology and a double-layer sand-control well completion pipe string. The double-layer casing sand-control well completiontechnology comprises the following steps that well drilling is conducted, specifically, a hydrate reservoir is drilled through a drilling bit; slit-cutting and sand blasting are conducted, specifically, a casing used for hydraulic slit-cutting is downed, and slit-cutting and sand blasting construction is conducted on a reservoir well section with the depth being less than 300 m below a mud line; and pre-filling sand control and well completion are conducted, specifically, a sand-control construction pipe string is hung and pre-filled by adopting a sand-control packer, and well completion is conducted. According to the double-layer casing sand-control well completion technology, a double-layer casing combined structure and the mechanical sand control technique are combined, a screen pipe with the high sand retaining precision is adopted, and the screen pipe is designed aiming at pilot production of a fine silt reservoir, so that the adaptive ability to the ground is high, and the mechanical sand-control cost is low; and not only can the risk that the screen pipe is buried caused by collapse of a deep-water ultra shallow stratum in the production test process be prevented, but also the risk of blocking of a production test pipe string due to large amount of sand production in the reservoir can be solved, and continuity of pilot production operation is ensured.