A computer-implemented method of a relay for cross-chain interactions in a unified blockchain network comprising a plurality of blockchain instances that are communicatively linked by two or more relays, the method comprising: storing, by a unified blockchain domain name server, for each blockchain instance of the plurality of blockchain instances in the unified blockchain network, a respective unified blockchain domain name that serves as a unique identifier of said each blockchain instance, wherein each unified blockchain domain name uniquely binds a blockchain domain name of a blockchain instance with a corresponding blockchain network configuration of the blockchain instance, wherein the blockchain network configuration of a blockchain instance is represented by a chain identifier that is different from the blockchain domain name with which it is bound, the chain identifier including a hash value of a genesis block of the blockchain instance as well as a network identifier that identifies the blockchain instance; wherein a unified blockchain domain name is used by and is recognizable globally by the blockchain instances in the unified blockchain network, and wherein all blockchain instances in the unified blockchain network follow the same domain name scheme and are assigned unique unified blockchain domain names; identifying, by the relay that is communicatively linked with a first blockchain instance and a second blockchain instance in the unified blockchain network, a blockchain domain name of a first blockchain instance, wherein the blockchain domain name of the first blockchain instance is a unique identifier of the first blockchain instance and uniquely corresponds to a chain identifier of the first blockchain instance in the unified blockchain network; identifying, by the relay, a blockchain domain name of the second blockchain instance, wherein the blockchain domain name of the second blockchain instance is a unique identifier of the second blockchain instance and uniquely corresponds to a chain identifier of the second blockchain instance in the unified blockchain network; receiving, by the relay from a node of the first blockchain instance, an access request for accessing the second blockchain instance, wherein the access request comprising the blockchain domain name of the second blockchain instance; identifying, by the relay, the chain identifier of the second blockchain instance based on the blockchain domain name of the second blockchain instance, wherein the chain identifier of the second blockchain instance indicates a blockchain network configuration of the second blockchain instance; and providing, by the relay, access to the second blockchain instance for the first blockchain instance based on the blockchain network configuration indicated by the chain identifier of the second blockchain instance, wherein the relay uses the blockchain network configuration to connect to the second blockchain instance, obtains a result requested by the first blockchain instance from the second blockchain instance, and returns the result requested by the first blockchain instance to the first blockchain instance. storing, by a unified blockchain domain name server, for each blockchain instance of the plurality of blockchain instances in the unified blockchain network, a respective unified blockchain domain name that serves as a unique identifier of said each blockchain instance, wherein each unified blockchain domain name uniquely binds a blockchain domain name of a blockchain instance with a corresponding blockchain network configuration of the blockchain instance, wherein the blockchain network configuration of a blockchain instance is represented by a chain identifier that is different from the blockchain domain name with which it is bound, the chain identifier including a hash value of a genesis block of the blockchain instance as well as a network identifier that identifies the blockchain instance; wherein a unified blockchain domain name is used by and is recognizable globally by the blockchain instances in the unified blockchain network, and wherein all blockchain instances in the unified blockchain network follow the same domain name scheme and are assigned unique unified blockchain domain names;