It is known that in nanocrystalline soft magnetic materials, Fe Si super grains with typical grain size of 10-15nm are the basis of excellent soft magnetic properties. Understanding the material microstructure does not automatically lead to a feasible and accurate material loss calculation. The limited material loss data provided by nanocrystalline core manufacturers, especially for frequencies above 100kHz, hinders the application of nanocrystalline materials to high-frequency magnetism. In this paper, the core loss density of nanocrystalline materials is measured for frequencies up to 500 kHz and fluid densities above 1 Tesla. The analysis and calculation will also help to formulate the core loss model required for magnetic design. Ft-3m was selected as one of the typical features and availability.