Lysine sulfate (LS) powder is at high risk of fire and explosion during its production, processing and storage. Considering its edible and nutritive values, the selection for its explosion inhibitor requires both excellent inhibition performance and environmental friendliness. The inhibition performance of a natural food additive of sodium phytate (SP) on LS dust deflagration is investigated by comparing it with ammonium polyphosphate (APP), which is a widely used flame retardant. The deflagration characteristics of LS mixtures with various mass fractions of SP and APP are recorded by high-speed photography and fine thermocouples. The combustion heat is tested by micro-scale combustion calorimetry. Thermal stability of samples are studied by using a synchronous thermal analyzer. The results show that the deflagration of LS dust is completely suppressed when the mass fractions of APP and SP increase to 2% and 8%, respectively. The corresponding inhibition mechanisms are proposed based on the dust deflagration macroscopic results and microcosmic analysis on thermal decomposition products and residuals. These findings may provide a solution to reduce the probability and damage of dust explosions. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.