The invention relates to a network on-line live line measurement method for the line parameter of a power system. A measuring center performs network on-line live line real-time measurement according to sets of computer networked data and networked instructions organized by a line parameter measuring system on the basis of a specific sequence. The method sequentially comprises the following stepsof: 1) accessing a global positioning system (GPS) signal to a data acquisition device in each transformer substation and correctly running; 2) requesting to establish transmission control protocol (TCP) connection, sending a device configuration information reading command and a real-time data command to the data acquisition device, receiving real-time data and establishing a real-time running chart; 3) actively retrieving the data acquisition device in each transformer station, monitoring the running condition of each line in real time and automatically measuring the line parameter; and 4) storing a line parameter measured value in a database. The data acquisition device which is put into operation and networked on site is utilized, and a new device is not required to be arranged, so that measurement workload can be obviously reduced, measurement cost is saved, power failure frequency is low, and power failure time is short; and the method is easy to operate, and safe and reliable.