The invention discloses an electric power data transmission system based on multilevel authentication and suspected attack isolation. The system at least comprises authentication servers and a data collection device, and a data transmission device is connected with the authentication servers and data centers through a network; one authentication server requests authentication from a superior authentication server until a top-level authentication server; the data center is located on the same level as the corresponding authentication server and extracts a historical authentication record of the authentication server; the data transmission device performs level-by-level authentication through the authentication servers and uploads the collected electric power data to the data center of the necessary level; and when a certain authentication server detects a suspected network attack, the authentication server immediately starts an isolation and defense mechanism, disconnects the connection relationship between the current level authentication server and the superior authentication server, isolates the current level data center, and sends real-time alarm reminding. The system provided by the invention performs multilevel authentication, thereby ensuring the safety, reliability and controllability of the system, a threat source is corrected and handled in time, and normal electric power operation is restored.