Artificial enzyme mimics are of current research interest owing to their remarkable advantages over natural enzymes. Herein, as a novel peroxidase mimic material, MIL-101(Cr)@PB was fabricated by encapsulating Prussian blue (PB) nanoparticles into the host matrix of MIL-101(Cr) via a facile and mild in situ growth synthetic strategy. The crystallographic characteristics, morphology, and porosity of the as-synthesized MIL-101(Cr)@PB composites were carefully studied using XRD, SEM, TEM, TGA, and BET. The results show that the synthesized MIL-101(Cr)@PB possesses a reproducible and impressive intrinsic peroxidase-like activity even under extreme conditions. Exploiting this, a colorimetric platform for screening xanthine oxidase inhibitors was constructed. We hope that this work will elucidate the applications of metal-organic frameworks as carriers for enzyme mimics and enable a wider application in drug screening.