The invention discloses a preparation method for nano-silver particles, and belongs to the field of preparation of the nano-silver particles. The preparation method includes the steps that rice is washed, water is added for stewing the rice, yeast powder and amylase are added to be stirred, and a reaction under the heat preservation condition is made; then glucose class matter is added to be mixed, and centrifugal separation is carried out after standing to obtain a supernatant for standby application; an ultrasonic container is opened, the infrared wave length is controlled, an ammonium chloride solution is added, the pH of the solution is adjusted to be alkaline through sodium hydroxide, and the solution, ethyl acetate and the like are mixed; carbon dioxide is led in from the bottom of the container for aeration, and silver nitrate and the supernatant for standby application are dropwise added while aeration is carried out; and standing filtering is carried out to obtain filtration matter, and warming evaporation is carried out after freezing to prepare the nano-silver particles. The preparation method has the beneficial effects that the preparing method is simple, the nano-silver particles are evenly scattered in the preparing process, solid-liquid separating is easy, and by-products are fewer; and obtained products are regular in shape and broad and even in size distribution, and the purity of the obtained product is more than 6% higher than those obtained through other methods.