The present invention provides a system and a method for internet-of-things identity authentication based on a blockchain which mainly solve the problem that identity authentication and data privacy are insufficient in the prior art. The system comprises a trusted third-party module, a device module, a user module and an intelligent contract module. The method comprises the steps of: system initialization, generation of a wallet file, creation of login device transaction, verification of the login device transaction to record a device module information sheet, creation of associated device transaction, verification of the associated device transaction to record user module information, creation of control device transaction, verification of the control device transaction to record the device state information, and quitting of a system. The system employs a decentration network to reduce the burden of a central server. The method improves the safety of user and device data, ensures theuser's anonymity, ensures that transaction information cannot be tempered and achieves user identity authentication for the device.