The invention provides a milk product for improving sleep; the milk product for improving sleep includes the raw materials: 30 to 99.69 parts by weight of milk, 0.01 to 0.5 part by weight of semen ziziphi spinosae or a semen ziziphi spinosae extract, 0.01 to 0.05 part by weight of vitamin E, and 0.0025 to 0.1 part by weight of sodium ascorbate. The invention also provides a preparation method of the milk product for improving sleep. The semen ziziphi spinosae or the semen ziziphi spinosae extract is added in the milk product for improving sleep, so through storage, no peculiar smell can be produced, and the taste and smell are better.