A power frequency parameter simulation system for a power transmission line and a control method thereof, the system includes a simulation main circuit (1), an interference power supply (2) and a procedure controller (3). In the system, a power frequency parameter of a 10 to 100 kilometers of 500 kV power transmission line is simulated in a lumped parameter manner; and the control method includes the following steps of: a step to detect the automatically zeroing during starting up, a step to control the reduction of the length of a simulation line and a step to control a simulation interference voltage. A long-distance power transmission line is realized to be moved into a room and be tested by means of the power frequency parameter test system, so the various inconveniences of on-site measurement are avoided.