The invention provides a flower-like ZnO nano material loaded with Ru nano particles, and provides a preparation method of the flower-like ZnO nano material and application of the flower-like ZnO nanomaterial in an acetone gas sensor. A crystal of the flower-like ZnO nano material is a flower crystal, and the average particle diameter of crystal particles is 5 [mu]m. The Ru nano particles are evenly loaded on the surfaces of ZnO nano particles. The flower-like ZnO nano material loaded with the Ru nano particles is adopted as a sensitive material, the high specific surface area of the flower-like ZnO nano material is applied, and the catalytic action of Ru on the surface of ZnO and acetone gas can be effectively utilized to improve the gas-sensitive response; and in addition, the acetone gas sensor is an improvement of an existing structure, a sensitive element is coated with the flower-like ZnO nano material loaded with the Ru nano particles, the characteristics of simple preparationmethod, low cost and large-scale production are achieved, and good detection performance is achieved on the acetone gas. In general, the process adopted is simple, prepared device are small in size, mass production is suitable, and thus important application value is achieved.