Abstract: Biological tests demonstrated that the inactivation of Nosema bombycis (N. bombycis) spores by chlorine dioxide (ClO2) occurs very fast and is highly sensitive. The lowest effective inactivation dosage and time was 15mg/mL for 30min. The inactivation of spores was additionally verified by using double color fluorescence stain and spore germination testing. A series of biological changes, including a large number of substrates that were leaked out from the spores included proteins, DNA, polysaccharide, K+, and Ca2+, occurred a short time after N. bombycis spores were treated with ClO2. In addition, the lipid of spores was disrupted and ATPase activity was inhibited, which resulted in the destruction of the inner structure of the spores. [Copyright &y& Elsevier]