Graphene, a plane object composed of carbon atoms, is a perspective material for nanoelectronics and spintronics because of its unique electron and magnetic properties. It was found that graphene reveals spin polarization effect, i.e. its magnetic features increase when crystal defects (vacancies and clusters of vacancies) are introduced. Systematic analysis is performed by ab initio simulation with the use of VASP program complex in order to state spin polarization dependence of graphene on the number vacancies in a cluster and on a cluster configuration.