The invention relates to a method for measuring the resistance coefficient of a secondary air register of a boiler accurately. The method includes the steps that 1, based on a modeling test principle,a secondary air distributing system test platform of the boiler is set up, is a cold-state modeling test platform, and comprises a fan, a secondary air box, a secondary air channel, the secondary airregister, a Venturi meter, a differential pressure transmitter and an inclinator; 2, through the Venturi meter, the air amount of a secondary air room and a spray port can be measured accurately, thepressure difference of the two sides of a secondary air register baffle can be determined through the differential pressure transmitter, and accordingly the resistance coefficient of the secondary air register is worked out; 3, through the inclinator, the opening degree of the secondary air register is measured, so that a curve of the opening degree of the secondary air register and the resistance coefficient of the secondary air register is obtained and is a feature curve of the secondary air register. Through the Venturi meter, the air amount and flow speed of the spray port can be measuredaccurately, so that the measurement result is more accurate; through the inclinator, the opening degree of the air register is measured, so that the measurement result is more accurate.