From the aspect of involutions,finite 2-groups with a maximal subgroup isomorphic to a generalized quaternion group are studied.By investigating the conjugacy classes of involution automorphisms and the number of involutions in the corresponding semi-direct products,a complete classification of such 2-groups is obtained.As a corollary,the number of involutions in such a 2-group is shown to be a completely invariant under isomorphisms.