Total-Routhian-surface calculations have been performed to investigate the shape evolutions of A∼80 nuclei: Zr80−84,Sr76−80, and Mo84,86. Shape coexistences of spherical, prolate, and oblate deformations have been found in these nuclei. Particularly for the nuclei Sr80 and Zr82, the energy differences between two shape-coexisting states are less than 220 keV. At high spins, the g9/2 shell plays an important role in shape evolutions. It has been found that the alignment of the g9/2 quasiparticles drives nuclei to be triaxial.