The legal nature of adding supplies can’t be interpreted well in traditional civil law, which engenders disputes in intellectual property law, so that the producers abuse intellectual property rights and infringe the interests of consumers. According to the principle of law and economics, declaration of intention in writing by the producers is a rule to divide the different legal natures of behaviors. And the transaction costs of this rule are low. Therefore, the legal nature of the adding supplies should depend on the declaration of intention in writing. In order to standardize the market order to protect the interests of consumers, distinguishing between the production and repair is necessary.