Magnetization distribution in nanocomposite Nd4.5(Fe,Cr)77B18.5 was studied by electron holography and computer simulation. In order to understand the detailed magnetization distribution, the magnetic flux distribution was calculated taking into account the magnetic charge or the stray field on the basis of magnetization models consisting of small magnetic dipoles and was compared with that in reconstructed phase images experimentally observed. Through the comparison, the characteristic feature in the distribution of the magnetization distribution in the nanocomposite magnetic materials was clarified, and the distribution was found to well correspond to their magnetic properties. It is pointed out that for understanding magnetization, the interpretation of reconstructed phase images should be done through computer simulation just as the analysis of high-resolution electron microscope images. Eventually, it was demonstrated that electron holography with computer simulation is quite useful to analyze detailed magnetization distribution in nanocrystalline magnetic materials at the nanometer scale.