The invention provides an ultrasonic preparation method of blue-light inorganic bromine-lead-cesium perovskite nanoparticles. The method comprises the following steps: S1, dissolving cesium acetate and lead acetate in a compound of oleic acid, oleylamine and octadecene by ultrasonic treatment to obtain a precursor solution; s2, adding benzoyl bromide into the precursor solution, and carrying out ultrasonic treatment for reaction; and S3, carrying out an ice-bath quenching reaction, adding ethyl acetate, and carrying out centrifugal separation to obtain the bromine-lead-cesium perovskite nanoparticles. The efficient luminous blue light CsPbBr3 nanoparticles are prepared through a simple and convenient ultrasonic synthesis method, and the method has the characteristics that the method is simple, large-scale preparation can be realized, the particle uniformity is good, the optical performance is excellent, and the like.