A boson approximation of nucleon pairs (not quasi-particle pairs) is considered with only s and d bosons. Besides one “ideal boson” energy, there are the residual interactions between the bosons which are assumed only as C(2)·C(2) and C(4)·C(4) forces in this paper. Our model reduces to the group theory of SU(3) on s-d boson by taking suitable amounts of the energy difference and of the quadrupole interaction between bosons. A gradual transition from vibrational to rotational pattern of the energy systematics and the wave functions with an increase of the order of the interaction strengths are found. The calculated reduced E2 transition rates give the order of the effective charge of a boson.