The invention provides a transmission line insulation resistance measurement method under strong interference. The method comprises the steps that a voltage regulator T is used to adjust the voltage of the low voltage side of a booster B; a voltmeter V is used to read the voltage value of the low voltage side of the booster B; according to the booster B ratio, the voltage value of the high voltage side of the booster B is determined; the tail end of a measured line Cz is open; a high voltage silicon stack D is used to apply direct current voltage of 30,000 to 50,000 volts on the head end pf the measured line Cz; a microampere meter mu A is used to read a leakage current value i; and a calculation value which is acquired through a formula R=u/i is the insulation resistance value of the measured line Cz. According to the invention, a leakage current measuring method is used; the direct current voltage which is much higher than the output voltage of an insulation resistance meter is applied on the measured line; the leakage current is read; the insulation resistance value is calculated through the formula; and the problems that the insulation resistance cannot be measured and the insulation resistance meter is burned, which is caused by large induction voltage and induction current and small output current of the insulation resistance meter, are prevented.