Let R be a ring and let H be a subgroup of a finite group G.We consider the weak global dimension,cotorsion dimension and weak Gorenstein global dimension of the skew group ring RσG and its coefficient ring R.Under the assumption that RσG is a separable extension over RσH,it is shown that RσG and RσH share the same homological dimensions.Several known results are then obtained as corollaries.Moreover,we investigate the relationships between the homological dimensions of RσG and the homological dimensions of a commutative ring R,using the trivial RσG-module.