A relay selection routing method based on direct communication of a terminal, applied to a base station, comprising: establishing a database of a topological structure of a direct communication terminal on a network side; when a channel quality of any path in the database of the topological structure is lower than a preset channel quality threshold, updating the database of the topological structure; when a direct communication service request is received, determining a data sending path and a destination relay node corresponding to the direct communication service request according to the database of the topological structure, sender information and receiver information of the direct communication service request and a preset selection principle; and establishing a direct communication data sharing network corresponding to the direct communication service request according to the data sending path and the destination relay node; the relay selection routing method further comprising: sending the database of the topological structure to the database of a superior topological structure of the network side through interfaces between base stations periodically or in a time triggered manner, and receiving the database of the superior topological structure sent by the database of the superior topological structure of the network side; and upon condition that there is no data sending path corresponding to the direct communication service request in a current service area corresponding to the network side, sending a path discovery request to the database of the superior topological structure of the network side; or upon condition that there is no data sending path corresponding to the direct communication service request in the current service area corresponding to the network side, broadcasting the path discovery request to other base stations; or sending the database of the topological structure to the other base stations through the interfaces between the base stations periodically or in a time triggered manner, and receiving the databases of the corresponding topological structures sent by the other base stations to realize a synchronization of information of the topological structures. establishing a database of a topological structure of a direct communication terminal on a network side; when a channel quality of any path in the database of the topological structure is lower than a preset channel quality threshold, updating the database of the topological structure; when a direct communication service request is received, determining a data sending path and a destination relay node corresponding to the direct communication service request according to the database of the topological structure, sender information and receiver information of the direct communication service request and a preset selection principle; and establishing a direct communication data sharing network corresponding to the direct communication service request according to the data sending path and the destination relay node; the relay selection routing method further comprising: sending the database of the topological structure to the database of a superior topological structure of the network side through interfaces between base stations periodically or in a time triggered manner, and receiving the database of the superior topological structure sent by the database of the superior topological structure of the network side; and upon condition that there is no data sending path corresponding to the direct communication service request in a current service area corresponding to the network side, sending a path discovery request to the database of the superior topological structure of the network side; or upon condition that there is no data sending path corresponding to the direct communication service request in the current service area corresponding to the network side, broadcasting the path discovery request to other base stations; or sending the database of the topological structure to the other base stations through the interfaces between the base stations periodically or in a time triggered manner, and receiving the databases of the corresponding topological structures sent by the other base stations to realize a synchronization of information of the topological structures. sending the database of the topological structure to the database of a superior topological structure of the network side through interfaces between base stations periodically or in a time triggered manner, and receiving the database of the superior topological structure sent by the database of the superior topological structure of the network side; and upon condition that there is no data sending path corresponding to the direct communication service request in a current service area corresponding to the network side, sending a path discovery request to the database of the superior topological structure of the network side; or upon condition that there is no data sending path corresponding to the direct communication service request in the current service area corresponding to the network side, broadcasting the path discovery request to other base stations; or sending the database of the topological structure to the other base stations through the interfaces between the base stations periodically or in a time triggered manner, and receiving the databases of the corresponding topological structures sent by the other base stations to realize a synchronization of information of the topological structures.