The invention discloses an electric catalysis reactor capable of reducing side reaction for wastewater treatment. The reactor consists of a pot body (1), an exhaust valve (2), a stirring mechanism (comprising a motor (3), a speed adjustor (4), a stirring shaft (5) and a stirring paddle (8)), a water inlet (5), a cathode/anode sheet group (7), a filter plate (9), a water outlet (10) and the like. A three-dimensional particle electrode is filled inside the reactor, and three-dimensional particles can be suspended between flat electrodes in a controllable stirring mode so as to effectively play a role in catalysis of the particle electrode, improve the generation rate of hydroxyl free radicals and reduce the occurrence of side reaction. Meanwhile, the controllable stirring mode improves the mass transfer effect of the solution, prevents dirt from being accumulated on the flat electrodes, and reduces the ohmic thermal resistance effect of electrodes. The electric catalysis reactor is applicable to degradation and purification treatment of high-concentration organic wastewater difficult to be biochemically degraded, high-chroma and high-ammonia nitrogen wastewater and oily wastewater, overcomes the defects that the prior equipment for treating the high-concentration organic wastewater has poor effect, high cost and the like, and has the advantages of simple and convenient operation, cleanness, thorough oxidation, stable treatment effect and the like.