The composite catalyst MnFe2O4-CR was prepared by hydrothermal method by loading MnFe2O4 on biomass gasification carbon residue (CR), characterized by SEM, XRD, XPS, BET and VSM, and utilized to activate permonosulfate (PMS) to degrade tetracycline hydrochloride (TC). The effects of different reaction systems, the mass ratio of MnFe2O4 to CR, dosage of PMS, dosage of catalyst, temperature, pH value, anion(HCO3–、H2PO4–、Cl–、NO3–) and humic acid (HA) on the degradation efficiency of TC in MnFe2O4-CR/PMS system were investigated. The stability and recyclability of MnFe2O4-CR were also investigated. The possible degradation mechanism of TC in MnFe2O4-CR/PMS system was investigated by free radical quencher experiments. The results showed that: When the mass ratio of MnFe2O4 to carbon residue is 1:2, the catalytic effect of MnFe2O4-CR is good. At 30 ℃, 30 mg MnFe2O4-CR catalyzes, 40 mg PMS, and the degradation efficiency of TC in TC solution with natural pH of 100 mL and 50 mg/L reaches 91.32% within 90 min. MnFe2O4-CR catalyst can be recovered by its magnetic properties. After 5 cycles, the degradation efficiency of TC degraded by PMS can still reach 82.90%, indicating that MnFe2O4-CR has good stability and reusability. Free radical quenching experiments show that SO4??, ?OH, 1O2 and O2?? are the main reactive oxygen species for TC degradation in MnFe2O4-CR/PMS system, and the corresponding catalytic degradation mechanism is proposed.