The invention relates to a losartan potassium gastric floating capsule, which comprises losartan potassium, PEG6000 (polyethyleneglycol), stearic acid, octodecyl alcohol, pre-gelatinized starch and mannite, wherein the losartan potassium is a powdery substance which is sieved with a 100-mesh sieve. A preparation method of the capsule comprises the following steps of: S1, mixing the PEG6000, the stearic acid and the octodecyl alcohol according to a certain proportion, heating to 64-66 DEG C, and smelting into a liquid; S2, heating the liquid mixture to 69-72 DEG C, and preserving heat for 9-11 minutes; S3, adding a proportional amount of losartan potassium into the mixture obtained in the step S2, keeping the temperature at 69-72 DEG C, and stirring uniformly; S4, adding a proportional amount of the pre-gelatinized starch and the mannite, and stirring uniformly; and S5, after the uniformity is qualified, filling in a hot state, covering a capsule cap, and cooling to the room temperature. The losartan potassium gastric floating capsule has the advantages that the medicament releasing time is long, the medicine taking times of a patient are reduced, the treatment compliance of the patient is enhanced, and the quality in a storage life is stable.