The invention discloses a leakage test control method and system for natural gas ignition for a large-scale thermal power generating unit. By means of the leakage test control method and system, the problem that when natural gas ignition is adopted for existing large-scale thermal power generating units, precise judgment of fuel gas leakage is needed urgently is solved. The method comprises the steps that after pressure stabilization of a natural gas mother pipe is completed, the current state of the natural gas mother pipe is maintained for two minutes, in the timing process, the existing airpressure value is subtracted from the air pressure value which is recorded before, and after the absolute value of the difference value is obtained, the result is divided by the air pressure value which is recorded before, so that the pressure change rate of a natural gas pipeline is obtained; and if the pressure change rate value is greater than 0.02, a natural gas leakage test failure mark is set, and if the pressure change rate value is less than 0.02 all the time till timing is ended, a natural gas leakage test success mark is set. By means of the leakage test control method and system, operation safety and stability of the unit are improved.