Fe-0-H2O2 Fenton-like process was effectively applied in the advanced treatment of citric acid wastewater. The important reaction conditions were optimized. When the initial pH was 3.0, H2O2/COD = 0.7* Fe-0/H2O2 = 3.29 (weight ratio), coagulation pH = 9.0, the COD removal reached to over 35% in 2 h. Especially, the reuse of Fe-0 was studied in details. The 2nd use of Fe-0 performed better than the pristine Fe-0 in COD reduction with a promotion of 28.78%, and the promotion maintained till the 5th reuse. During the recycling and reusing process, Fe-0 kept good stability in reaction activity though gradually covered by a filmy oxidation layer on its surface. In order to examine the changes of Fe-0 after several uses, samples were characterized by TEM, HRTEM, SEM, EDS, XPS, and XRD. It was found that the surface of Fe-0 particles was smooth before use while rough after reactions. Though it generated a filmy oxidation layer covering on the Fe-0 surface, the intensity of peak at 110 crystal planes kept strong and distinct, detecting by XRD. After 5 times of use, the EDS spectrum showed only about 7.35% more of oxygen content was increased on Fe-0 surface. XPS spectra demonstrated that Fe(OH)(3) and FeOOH were the main oxidation production generated on surface of Fe-0 particles during the Fenton-like reaction. The existence of this oxidation layer did not weaken the effect of Fe-0-Fenton process, but strengthened it. The presumed reaction mechanism of Fe-0-Fenton was proposed, including the reaction process and the materials conversion.