Radon is the most accessible radioactive gas in life. The radon in ambient air mainly comes from the soil. In order to ensure the accuracy and validity of the measurement of radon concentration in the soil, the paper discusses the influencing factors of the measurement of radon concentration in the soil through the controlled variable method. On the basis of familiarity with the principle of measuring the concentration of radon in the soil, using the radon meter to study the influence of the measurement depth, measurement period, soil type, fault and other factors on the measurement results in the actual measurement process, experiments show that the measurement depth maintained at 60 - 80 cm is appropriate; the measurement period has little effect on the measurement results, but measurement should be avoided in rainy days; different soil types have different effects on the measurement results, and the density and gap of the soil should be comprehensively considered; the radon concentration at the fault location will be obviously elevated.