The variation of crystal system and conduction behavior of perovskite superconductor, BaPb0.75Bi0.25O3-delta, with oxygen deficiency was studied. The crystal system of BaPb0.75Bi0.25O3-delta changed from orthorhombic through tetragonal to pseudo-cubic as delta increases. The superconducting transition was observed in the specimens with the orthorhombic phase. Oxygen-deficient specimens with tetragonal or pseudo-cubic symmetry did not show a superconducting transition. The increase in electrical resistivity was also observed with an increase in delta, which suggested decrease of electron carrier mobility with the increase in delta. This effect of oxygen deficiency on conduction behavior of BaPb0.75Bi0.25O3-delta showed contrast with those of the superconducting cuprates, in which carrier concentration is affected instead of carrier mobility. The difference in the effects of oxygen deficiency on conduction behavior could be attributed to the difference of crystal structure between BaPb0.75Bi0.25O3-delta and superconducting cuprates.