The invention discloses a soap containing yak milk components and a preparation method thereof. The preparation method comprises the following steps: mixing Tibetan yak butter, sea-buckthorn seed oil, coconut oil, palm oil and olive oil, heating the mixture in water, keeping the temperature of the oil mixture in the range of 30-45 DEG C; mixing sodium hydroxide with water, stirring the mixture until the sodium hydroxide is completely dissolved, maintaining the alkali liquor temperature between 30 DEG C and 45 DEG C; slowly pouring the oil mixture into the alkali liquor, mixing and stirring the mixture until the soap liquid is in a thick paste state, and when the saponification reaction is complete, adding a perfume and a preservative into the mixture, then slowly adding yak milk, continuously stirring, and finally pouring the soap liquid into a mould to be formed. The preparation method disclosed by the invention has the beneficial effects that (1) the preparation method is simple and practical, and the production cost is low; the physiological activity of the yak milk is greatly protected, and the preparation method is suitable for popularization and application; (2) the content of the yak milk in the soap is 5%-45% and the physiological activity is strong, the soap has the effects of cleaning, whitening, freckle-removing, skin nourishing, anti-aging and the like.