Magnesium based composites MgH2 + X (X=Ti, Co) were synthesized by ball milling in an argon atmosphere using stainless steel vial and balls. The crystallographic behavior of the resulting powders was examined by XRD. Thermal stability and hydrogen desorption properties were investigated by thermal analysis methods. In order to obtain a deeper insight into bonding mechanisms of the transition metal in MgH2 relaxed structure, ab initio electronic structure calculation of MgH2 + X (X=Ti, Co) was performed using Full Potential Linearized Augmented Plane Wave method, implemented in WIEN2K code. DOS analysis, confirmed by DTA measurements, resulted in the conclusion that, in the composite, in comparison to MgH2, the bonding Mg-H was weakened, on account of the shortening of interatomic distances hydrogentransition metal.