The present invention provides a method for removing pentavalent antimony contaminants in water without adding a DC power supply and also provides a fuel cell capable of removing the pentavalent antimony contaminants in water by utilizing self-generated electric energy. A technical solution of the present invention is as follows: waste water is pumped into a reactor for reaction after a pH value of the waste water containing the pentavalent antimony contaminants adjusted to 3-6.5; the inside of a reactor is an anaerobic environment; and an iron anode is arranged in the reactor, a through hole is formed in a side wall of the reactor, a cathode for reducing oxygen by electrons and protons sealed and inlaid in the through hole, and a resistor is connected between the iron anode and the cathode in series. The present invention is suitable for a water treatment technology.