The invention discloses a GIS (Geographic Information System)-based heat supply network leak detection system and a method thereof. The GIS-based heat supply network leak detection system comprises a data collection and monitoring subsystem, a real-time service subsystem, a database and a GIS platform management subsystem. The data collection and monitoring subsystem is used for collecting and transmitting leak monitoring data of fixed monitoring points of a heat supply network. The real-time service subsystem is used for communicating with the data collection and monitoring subsystem to obtain the leak monitoring data and store the leak monitoring data in the database, and analyzing the leak monitoring data. The database is used for storing the leak monitoring data, digital map data and heat supply network pipeline data. The GIS platform management subsystem is used for communicating with the database and displaying the leak monitoring data and the influence area of an accident of an accident monitoring point on a heat supply network digital map according to second leak alarming information. Compared with the prior art, the GIS-based heat supply network leak detection system can timely and accurately find the heat supply network leak accidents, a GIS platform can accurately position the leak accidents and display the accidents on the map, and the leak accident information can be timely supplied to corresponding staff members.