The recombinant protein was used in this paper to assess the safety of Cry1Ab/Ac protein. The result obtained from structural and functional equivalence assay explain that the recombinant protein produced from E. coli was an appropriate substitute for the extracted protein directly from genetically modified rice. Heat stability study showed the same recognition of the heat-treated and the native proteins by anti-Cry1Ab/Ac antibodies indicated that the conformational changes associated with denaturation did not affect the epitope accessibility which means that the epitope homology search, which showed no similarities with known allergenic epitopes, has a major weight of evidence in this safety assessment. To have a direct assessment of the protein toxicity in mammals, an oral acute study in mice is used for evaluating the safety of the Cry1Ab/Ac protein. In this study, the mouse acute oral LD50 was >5000 mg kg−1 (body weight), which belongs to practically non-toxic grade. The results are coincidence with Delaney et al. (2008) which showed the results from acute mouse toxicology studies with proteins in GM crops were: Cry1Ab > 4000 (oral) and Cry1Ac > 4200 (oral). These results indicated that the Cry1Ab/Ac protein has no harm to human beings and animal.