A standard in-beam γ-spectroscopy experiment for 188Pt is performed via the 176Yb(18O,6n) reaction at beam energies of 88 and 95 Me V,and the level scheme for 188 Pt is established.Prolate and oblate shape coexistence has been demonstrated to occur in 188Pt by applying the projected shell model.The rotation alignment of i13/2neutrons drives the yrast sequence changing suddenly from prolate to oblate shape at angular momentum 10h,indicating likely a new type of shape phase transition along the yrast fine in 188Pt.