A hierarchical Co3O4-Bi2O3 composite was first prepared via an adsorption-calcination method using a bismuth-based MOF (Bi-BTC) as the precursor and substrate. In the composite, Co3O4 nanoparticles are loaded on the outer layer of Bi2O3 rods derived from Bi-BTC and show a uniform honeycomb-like morphology. In dyes degradation tests, the Co3O4-Bi2O3 composite exhibits much better peroxymonosulfate (PMS) activation performance in RhB degradation than pure Bi2O3 or Co3O4. The Co3O4-Bi2O3/PMS system also shows high performance for various azo dyes and maintains good catalytic performance at wide pH range. Besides, the good chemical stability of Co3O4-Bi2O3 ensures it good reusability in four recycling tests. XPS and electrochemical analysis indicate the interaction of Bi species promotes the activation capacity of Co3O4 nanoparticles. The results of radicals quenching tests and ESR analysis reveal the singlet oxygen and superoxide radicals are the dominant functional radical species in Co3O4-Bi2O3/PMS system and subsequently a reasonable activation mechanism is proposed.