The invention discloses a method for predicting the water permeability of a cement-based material based on a low-field magnetic resonance technology, and relates to the technical field of cement-basedmaterial testing. The aim of the invention is to provide a method for accurately measuring the water permeability of the cement-based material. The method comprises the following steps of: 1, measuring a transverse relaxation time spectrum of a saturated cement-based material test piece by using a low-field magnetic resonance relaxation technology; 2, preparing a cement-based material test pieceof which the surface is adsorbed with a single-layer water molecular film by utilizing an isothermal adsorption/desorption equilibrium method; 3, measuring the surface relaxation rate of a single-layer water film in the cement-based material test piece by using a low-field magnetic resonance pulse echo technology; 4, combining the transverse relaxation time spectrum and the surface relaxation rateto obtain a pore size distribution curve of the cement-based material in a water saturation state; and 5, predicting the water permeability of the cement-based material based on the pore size distribution curve of the cement-based material in the water saturation state. By adopting the method, the water permeability of the cement-based material can be more accurately predicted.