Accurate measurement of rainfall with high spatial and temporal resolution have important significance in meteorology, hydrology, agriculture, environment, flood warning and weather forecasting, etc. Based on the rain-induced power-law attenuation, an inversion method of the path rainfall intensity is proposed by using a microwave link. Starting from the atmospheric gas absorption attenuation model, a correction model of rainfall effective attenuation and a rainfall inversion model for line-of-sight microwave links are proposed, based on the microwave rain attenuation characteristics and raindrop size distribution statistics. A line-of-sight microwave link is designed and used to measure the rainfall, and the path average rain rate is inversed by means of rainfall inversion model, which is compared with a disdrometer. Results show that the correlation coefficient of rain rate inversed by microwave link with that of disdrometer is higher than 0.6 mostly, and the maximum value is 0.9647; the error of the accumulated rain amount is less than 0.5 mm, and the minimum value is 0.0827 mm; the relative error of the accumulated rain amount is less than 15%, the minimum value is 3.3415%. Experiments confirm the feasibility and accuracy of rainfall inversion obtained using a microwave link.