The paper deals with identification of the fundamental equation of batch grinding which is used frequently for describing the kinetics of batch grinding processes. The fundamental equation is set up by the modification of a usually used selection function known from literature. In this method of identification, application of a new, recently developed distribution function, called hyperbolic tangent distribution family, plays an important role. The parameters of the fundamental equation are determined by means of estimation of parameters of a hyperbolic tangent distribution function which approximates the analytical solution of the fundamental equation. The method is illustrated by presenting a practical example.