This paper refers to determination of magnetic nanoparticles distribution as a function of both magnetic moment µ and energy barrier EB. The original analysis consists in a numerical analysis of experimental M(H) curves determined at two different temperatures and is based on the Stoner–Wohlfarth model. As it was shown, the applied “simulated annealing (SA)” calculation algorithm with additional entropy maximum condition allows characteristic distribution profiles to be determined. Moreover, from the temperature shift of the profiles, the real positions of their homological points in µ–EB space can be calculated. It should be emphasized that the novel approach does not require any preliminary assumption of a distribution shape and number of components. The proposed magnetic characterization was tested with the use of computer-generated as well as experimental M(H) curves. The obtained results confirm the efficiency of the method and its usefulness in analysis of hard magnetic powder systems.