Bacterial cellulose (BC) is a natural product with multiple properties， which has been utilized in tissue engineering. However， cell adhesion and proliferation are reported to be weaker on native BC， providing less support compared to other types of biomaterials， like collagen. To increase the biocompatibility and the medical performance of BC， in situ modification is used to add carboxymethyl group to BC. By partially changing the structure and physical properties of BC， carboxymethylation significantly increases cell affinity and viability， especially on the initial cell adhesion. Furthermore， in the in vivo implantation， the tissue reaction shows that carboxymethylation significantly increases the biocompatibility of BC， exhibiting better tissue condition and a lower inflammatory reaction which are proved through HE staining and immunohistochemistry. The data prove that in situ carboxymethylation is a simple and direct way of improving the performance of BC in medical applications.