The invention discloses a method for evaluating porosity characteristic of regenerated concrete of building waste. The method is characterized in that the method is proposed under a reasonable assumption condition on the basis of law of conservation of mass, Gauss-Markov theorem and Fermat Lemma, and comprises the following steps of obtaining material from a material yard; screening the regenerated aggregate of the building waste, measuring the mass of the saturating surface of the aggregate during drying and the mass after drying, and preparing a group of regenerated concrete samples; standardly curing the samples, and putting into a water bath box, wherein when the mass difference of the sample is no more than 0.1% of the mass of the sample, the sample absorbs water to saturate; for the water absorbing saturating mass of the sample, using a Me(t) and t relationship model regressed by a Gauss-Markov method. The method has the advantages that the porosity water in the regenerated concrete can be distinguished from the water content of regenerated aggregate, the relationship of drying time and water loss amount of the regenerated concrete is accurately measured, the effective porosity is solved, and the theoretical support is provided for using the regenerated aggregate to prepare the water absorbing and permeating concrete.