Abstract: ObjectiveTo study the pre-chemical reaction between Se and Cd by multiple injection administration of Se and Cd in the abdominal cavity of rats.MethodsTo deter mine the situation of poisionous stuffmixing and reaction by using the prevention of Se to the toxicity of Cd in different administration groups,together with the experiment of external chemical raction of Se-Cd and internal mix ing of I₂-starch within abdominal cavity.ResultsSe and Cd injected simultaneously in abdominal cavity from right and left site could be mixed very quickly and CdSeO₃ was formed by the chemical reaction.Due to the low solubility of CdSeO₃,Cd absorbed by rats was remarkably decreased and the pseudo-prevention effect was observed.ConclusionAvoiding the internal pre-chemical reation while two or more test agents are administrated by injection.