The self-consistent ab initio calculations, based on density functional theory (DFT) approach and using full- potential linear augmented plane wave (FLAPW) method, are performed to investigate both electronic and magnetic properties of the MnAs compounds. Polarized spin and spin-orbit coupling are included in calculations within the framework of the ferromagnetic state between two adjacent Mn atoms. The ferromagnetic and antiferromagnetic ener- gies of MnAs systems are obtained. Magnetic moment con- sidered to lie along (001) axes is computed. The obtained data from ab initio calculations are used as input for the high-temperature series expansion (HTSE) calculations to compute other magnetic parameters. The exchange inter- actions between the magnetic atoms Mn-Mn in MnAs are given using the mean field theory. The HTSEs of the mag- netic susceptibility with the magnetic moments in MnAs