The utility model discloses an on -line monitoring system of transformer substation, this monitoring system be including the terminal equipment who produces the monitoring data, with terminal equipment carries out communication connection, receives and the storage the backstage management system of monitoring data, and with the backstage management headtotail shows the monitoring data is right according to user instructions analysis processes's PC end is carried out to the monitoring data. On -line monitoring system of transformer substation can save the monitoring data to carry out analysis processes to historical monitoring data, saved the manual work greatly for prior art, promoted work efficiency, be favorable to carrying out more effectual management to the power equipment of transformer substation.