〔Abstract〕 Objective To explore the feasibility of CS-BC composite membrane as guided bone regeneration(GBR) membrane by preparing chitosan(CS)-bacterial cellulose(BC) composite membrane, and testing the mechanical strength of the composite membrane both in dry and wet states as well as evaluating its cytocompatibility. Methods The CS solution and BC solution were mixed in different weight ratios and were dispersed evenly by ultrasonic. Pure CS membrane and composite membranes with different weight ratios of CS and BC(10 ∶1, 10 ∶3, 10 ∶5, 10 ∶7 and 10 ∶9) were prepared by self-evaporation process. Thereafter, the fabricated membranes were immersed into sodium hydroxide ethanol solution to remove the acid. The tensile strength of the as-fabricated membranes under dry condition and under hydration were measuredviamechanical universal testing machine(n=6). The microstructures of the composite membrane with the highest tensile strength were observed by scanning electron microscopy(SEM) and transmission electron microscopy(TEM). To characterize the chemical composition of the composite membrane, Fourier transform infrared(FTIR) spectrometer and X-ray diffraction(XRD) were used. CCK-8 assay was carried out to evaluate the survival rate of cells in the control group(without any membrane), the pure CS membrane group and the composite membrane group with maximum tensile strength(n=5) after cocultured with rat bone marrow stem cells(RBMSCs) for 1, 4 and 7 d. Results The cross-section of the composite membrane displayed ordered layer structure after introducing BC into CS matrix. The results of FTIR and XRD indicated the existence of BC in the composite membrane. The tensile strength of the CS-BC composite membrane increased first and then decreased with the increase of BC ratio. The tensile strength of the composite membrane reached the highest in dry and wet states when the weight ratio of CS and BC is 10 ∶7, which were almost(204.7±63.0) MPa and(44.4±6.4) MPa respectively. After cocultured with RBMSCs for 1, 4 and 7 d, there was no significant difference in the number of cells among the pure CS group, the CS-BC composite membrane group and the blank control group. Conclusion When the weight ratio of CS and BC is 10 ∶7, the tensile strength of the composite membrane are the best both in dry and wet state and the cell compatibility is excellent.