Studies of the dHvA effect have been made on NbO single crystals grown by a zone melting techniques and 13 separate frequency branches ranging from 5.2×106 G to 1.2×108G have been observed. To understand the origin of the dHvA frequencies, we have made a self-consistent band structure calculation. Most experimental frequencies are found to be assigned to the extremal orbits on the calculated Fermi surfaces. There is good qualitative agreement between experiment and calculation, but some quantitative discrepancies still exist. We also report some physical properties, i.e., electrical resistivity, superconducting transition temperature, and electronic specific heat, of this high-quality NbO crystal.