The shape coexistence in188Pb is investigated in terms of the projected shell model. Analyzing the experimental data with the calculated results, it is shown that the three shapes, sphere, oblate and prolate, coexist with each other in the low-lying excited states. The prolate band exhibits a mixture between two kinds of multi-particle-hole configuration. The mixing is discussed and the mixing coefficients are given, meaning the vi12/2 pair alignment happens gradually in this case. The oblate (ϕh 9/22p2h) band structure is predicted and the 2+ prolate state is in the range of 804-880 keV.