The invention provides a multilayer gravel packing method and tool. The method comprises the following steps in sequence: A. a) sinking a disposable multilayer gravel packing tool; and b) inserting insertion positioning seals and automatic guide shoes into sump packers; B. c) setting top packers, examining seal of the top packers and releasing the top packers; and d) setting interlayer isolation packers on the lower layer and examining seal of the interlayer isolation packers; and C. e) packing a lower oil layer; and f) carrying out reverse circulation; repeating the substeps d), e) and f), namely setting the interlayer isolation packers on the upper layer and examining seal of the interlayer isolation packers, packing a middle oil layer and carrying out reverse circulation; and repeating the substeps e) and f), namely packing an upper oil layer and carrying out reverse circulation. The tool is characterized in that a service tool is installed in an outer tube column, wherein the outer tube column comprises the top packers and bush sealing bores, bushes, sealing bores, sliding sleeves, short sections, sieve tubes, the interlayer isolation packers, the insertion positioning seals, the sump packers and the automatic guide shoes which are connected below the top packers; and the service tool comprises setting tools and wash tubes, a central tube, a packing conversion tool, pressure measuring assemblies, rotary positioning tools, one-way sliding sleeve switch tools, two-way sliding sleeve switch tools and bottom isolation seals which are installed below the setting tools.