The invention provides a duloxetine hydrochloride medicament composition, an enteric sustained release preparation and a preparation method thereof. The enteric sustained release preparation comprises the following components in parts by weight: 5-40 parts of duloxetine hydrochloride, 35-65 parts of sodium alginate, 5-20 parts of calcium salt, 15-35 parts of filler and 0.5-20 parts of lubricant. The medicament composition and the enteric sustained release preparation provided by the invention are hardly released under the gastric acid condition, so that a main medicine is prevented from being damaged in a stomach, no functional sustained release coating is needed to control medicine release, no enteric sustained release material is needed, only high-velocity sodium alginate and other medical auxiliaries are used, the enteric effect is achieved by adjusting the ratio, meanwhile the sustained release function is achieved, the medicine is effectively prevented from being damaged by the gastric acid environment, and the stability of the medicament inside a body in the absorption process is maintained.