Rumors related to products affect the individual judgment on the product and the purchase desire, and then spread to the market demand for products in the entire supply chain.Considering the individual's emotion and his judgment on rumors, immune persons R in classical rumor spreading model were subdivided into blinded persons R_a and sober-minded persons R_d.Individuals of the two states both know rumors but don't spread rumors.The difference is that R_a are fooled by rumors completely, and they don't buy the related products, while R_d, as sober-minded persons, don't believe rumors and continue to purchase the products.A rumor spreading model CISR_aR_d was constructed in accordance with the system dynamics, the model's stability was certified, and the rumors' restraining effect on product demand was investigated.On this basis, a numerical simulation was carried out.The result shows that rumors related to products restrict the market demand seriously, and positive publicity in response to rumors attack made by merchants has its positive significance to the recovery of product demand.