Considering the Coulomb potential and the exchange action, electronic structure, band structure and magnetic properties of the compound Ni4PrB within the local spin-density approximation (LSDA) and the LSDA+U approximation are studied through numerical simulation. The simulation results show that this system is a metallic semi-conductor and has Pr-Ni ferromagnetic coupling. The added Coulomb U effect can strongly affect magnetic properties and stable structure, and the total magnetic moment is provided by the local Ni magnetic moment before adding U effect, when the U effect is added to the system, the total magnetic moment is provided by the local Pr magnetic moment, and the system has a high structure stability. So U effect affects strongly the strong correlation, then it can describe reasonably the strong correlation and the exclusion effect caused by the spin exclusion.