The invention discloses an oxybutynin hydrochloride sustained-release capsule and a preparation method thereof. The oxybutynin hydrochloride sustained-release capsule is prepared from, by weight, 6.8% of oxybutynin hydrochloride, 86.8% of sugared pills, 1.3% of hydroxypropyl methylcellulose, 0.3% of 35% dimethicone emulsion, 3.7% of aqueous ethylcellulose dispersion, 0.8% of sebacic acid dibutyl ester and 0.3% of talcum powder. By means of the oxybutynin hydrochloride sustained-release capsule, effective blood concentration can be kept in vivo, no peak valley phenomenon is caused, side effects caused when the blood concentration is too high are relatively reduced, and meanwhile the non-treatment effect caused when the blood concentration is too low is reduced; the number of medicine taking times in each day is decreased, and the medicine taking compliance of patients is improved.