Abstract: According to the measurement method in Appendix A of JJF 1815-2020 " Calibration Specification for Class Ⅱ Biosafety Cabinets ", the source of uncertainty components of each standard was analyzed, and the measurement uncertainty evaluation method for biosafety cabinet personnel, product, and cross-contamination protection (potassium iodide method) has been successfully established, and the uncertainty of the measurement results was evaluated. The extended uncertainties of personnel protection, product protection, and cross-contamination protection of biosafety cabinets were 34%, 33%, and 32%, respectively, with the inclusion factor k all being 2, which suggests that they can be used for the standardization of methods for traceability and measurement uncertainty assessment of related parameters.