The interacting boson model with one- and two-boson excitation from the core is considered. This model is applied to the N=88 nuclei, 154Dy and 158Yb, which have been found to have a change from prolate through triaxial to oblate shape at high spin region experimentally. It was found that the energy levels of 154Dy and 158Yb can be reproduced very well. The backbends of the moment of inertia can be also reasonably described.