Tendon-derived type I collagen is an essential biomaterial for various biomedical devices due to its inherent bioactivity and favorable environment for cells. Correspondingly, microbial and endotoxin contamination can be easily introduced during the collagen extraction process, which is generally overlooked in fundamental scientific research, especially the endotoxin residue. Conventional approaches for mitigating endotoxin exhibit limited effectiveness when applied to biomacromolecule products because of viscosity, clogging, and diminished bioactivity. In this study, we developed a bifunctional sheet that can simultaneously reduce the microbe and endotoxin contamination in collagen solution by co-incubation and subsequent magnetic separation, avoiding the issues of blockage and bioactivity impairment. The bifunctional sheet was successfully fabricated by modifying the magnetic graphene oxide with histamine. Collagen products treated by sheets exhibited reduced microbial and endotoxin contamination while maintaining their bioactivity for encapsulated cell growth. Additionally, inflammatory stimulation of collagen was decreased in vitro and in vivo after treatment. This work may present a facile approach for diminishing microbe and endotoxin residues in collagen products in basic research, obviating the non-essential use of a sterile workshop and facilitating the development of tissue-derived collagen research.