The invention discloses a preparation method of a mosapride citrate stomach buoyant sustained-release pellet. The mosapride citrate stomach buoyant sustained-release pellet is formed by a drug-loadedpellet core, and a gas-generating layer and a retardation layer which wrap the pellet core, the inner layer of the pellet is a light-weight pellet core, the outer layer of the pellet is wrapped with acontrolled-release polymer material, and the middle layer of the pellet is the gas-generating layer produced from NaHCO3 and HPMC used as an adhesive. When the pellet meets a release medium water, the pellet can be quickly hydrated and expand, the pellet and CO2 gas produced by NaHCO3 in the gas-generating layer are prevented from overflowing by the retardation layer, so the pellet can float fora long time, and the release of the drug from the core is controlled; and the mosapride citrate stomach buoyant sustained-release pellet has the advantages of good roundness, good buoyancy in vitro, realization of a 8 h buoying rate reaching 80% or above, and good sustained-release characteristic.