The invention discloses a treatment method for high-concentration wastewater difficult to degrade. At the pretreatment stage, various pollution substances in wastewater are greatly degraded through the microelectrolysis reactor, Fenton reactor and multifunctional wastewater treatment machine combined mode, and meanwhile biodegradability of wastewater is regulated; at the biodegradation stage, most of pollution substances in wastewater can be treated and degraded by adopting the A2O and AO treatment process, conducting anaerobic, hypoxia and aerobiotic one-time biochemical and anaerobic and aerobiotic two-time biochemical treatment on wastewater and conducting ceaseless closed-loop inner circulation in the biochemical interior; at the after-treatment stage, by means of the multifunctional biological filter, multi-medium filtration and biological activated carbon adsorption combined treatment process, remaining pollution substances in wastewater can be degraded to the maximum extent or degraded after being adsorbed, and finally discharge water reaches the qualified emission target. The method is wide in application range, good in treatment effect and low in running cost, physical and biological treatment of high-concentration wastewater difficult to degrade is enhanced, and pollution of wastewater to the environment is reduced.