The invention discloses a microwave rain attenuation law based artificial rainfall experimental method with an adjustable link length, including the following steps of: 1) designing and calculating rainfall intensities in different return periods to form an experimental rainfall process, and simulating artificial rainfall by using an artificial rainfall hall; 2) building a corner reflector to dynamically adjust the microwave link length; 3) installing an experimental microwave device, and selecting a microwave link with a specific microwave frequency band as an experimental link; 4) using a self-recording rain gauge to obtain measured data on the experimental link under different rainfall intensities; and 5) according to the measured data, obtaining a whole process of the experimental rainfall intensity change, and analyzing and calculating the microwave rain attenuation law.