The invention discloses oil-in-water coffee milk beverage and preparing method thereof, wherein the oil-in-water coffee milk beverage is composed of the following components, by weight: 10-50 parts of coffee, 20-100 parts of water, 5-20 parts of milk, 5-20 parts of cream, 2-15 parts of nanometer clay, 1-2 parts of flower, 1-2 parts of fruit and 1-10 parts of sugar. The oil-in-water coffee milk beverage has existence of oil-in-water system and thickening effect of nanometer clay, which can effectively prevent milk composition from sedimentation. The beverage has low cost and simple process. Existence of flower and fruit can provide fragrance and nutrient at the same time. Nanometer clay is beneficial to intestines and stomach, and prevents diseases such as diarrhea.