To gain an in-depth understanding of the relationship between capillary suction and moisture content in cement-based materials, a prediction model for capillary suction in cement-based materials considering pore fractal characteristics was developed based on the fractal geometry approach and the capillary theory. This model establishes a fitting relationship between the fractal model parameters and the sample mix proportion, enabling rapid prediction of capillary suction for cement-based materials with different mix proportions. Verification experiments measuring pore size distribution were conducted based on the relative humidity method. The results indicate that samples with different mix proportions (water, ash, and sand) exhibit significant fractal characteristics, which could be well described by the Menger sponge fractal model. The deviation between the predicted results of the capillary suction model and the experimental test results was mainly within ±20%, demonstrating that the model can accurately predict the relationship between capillary suction and moisture content in cement-based materials.