Photoelectrocatalytic (PEC) degradation efficiencies of a suspended TiO2 and Ti electrodes composite system in different ammonium salt solutions were investigated. Electrolyte type and concentration as well as the applied potential on the Ti electrodes had significant effects on photoelectrocatalytic degradation and electro-degradation efficiencies. PEC degradation and electro-degradation of methyl orange increased with increasing applied potential and electrolyte concentration. PEC degradation is much more powerful than electro-degradation. PEC degradation efficiency in (NH4)3PO4•3H2O solution is the highest 93.4%, whereas the efficiency in NH4Cl solution shows the worst 73.1%, which is even less than that of photocatalytic process alone. PEC degradation efficiencies in (NH4)2SO4 and NH4HCO3 solutions are 88.8% and 85.9% respectively, indicating no noticeable improvement compared with photocatalytic process.