Tobacco FI protein was purified by dextran gel chromatography, component identification and mass spectrometry were performed by SDS-PAGE and PAGE electrophoresis, and FI protein was subjected to mouse limit test. The results showed that:（1） FI crude protein was obtained by heat sink method, and 3 components were separated and collected by gel chromatography. In the gel electrophoresis diagram, it is clear that component 1 has two subunits, 55 kD and 13.6 kD, respectively. After comparing with the standard, it is determined that component 1 is FI protein.（2） In the results of mass spectrometry analysis, the FI protein contains 20 amino acids and 8 essential amino acids for the human body, and it has reached the FAO/WHO high-quality protein scoring standard.（3） Limited experiments showed that FI protein had no significant effect on the clinical behavior, body weight and organ coefficient of mice（P＞0.05）, indicating that FI protein had no inhibitory effect on the growth and health of mice, and it was basically non-toxic. In this experiment, the amino acid composition of FI protein was evaluated and analyzed through protein profile and mouse limit test, which clarified the nutritional value and food safety of FI protein, and provided a theoretical basis for the multi-purpose development and utilization of tobacco FI protein.