On the basis of studying the denitrifying capability of batch cultured Alcaligenes faecalis (A.faecalis), the electrochemical method was applied by poising different cathode potentials (-0.15 V, -0.06 V, +0.06 V vs. NHE) to simulate the energy of photoelectrons from conduction bands of semiconducting minerals. Based on the results obtained, the authors studied the influence of exogenous electrons with different energy levels on the growth and denitrification capability of A. faecalis in the electrochemical system. The result showed that in the case of batch culture, A. faecalis could reduce nitrite significantly under aerobic or anaerobic conditions, rather than reducing nitrate. In simulated photoelectron systems, the formation of cathodic biofilms with denitrification activity on the graphite electrode was observed at all three cathode potentials (-0.15 V, -0.06 V, +0.06 V vs. NHE). Quantitatively, the bacteria was obviously colonized on the cathode poised at -0.15 V, the removal rate of nitrate by A. faecalis was simultaneously the highest (52% after 10 d), compared with 30.5% reduction rate of NO₃^- in the -0.06 V system. Much fewer bacteria were attached sparsely to the electrode surface when the poised potential was at +0.06 V, resulting in the lowest removal rate of 10.6%. In the sterile systems (three cathode potentials without bacteria), the concentration of NO₃^- only decreased a little. The results of this study indicate that photoelectrons with different energies from semiconducting minerals influence the metabolism and denitrification capability of heterotrophic microbe-A. faecalis.