The invention discloses a groundwater extraction effectiveness evaluation method for a low-permeability soil layer. According to the method of the invention, the effective extraction rate delta and effective water holding rate S of a site to be repaired are defined and calculated; and the effectiveness of groundwater extraction is evaluated according to the calculated effective extraction rate delta and effective water holding rate S according to an evaluation principle that the effectiveness of groundwater extraction is in direct proportion with the effective extraction rate delta and an evaluation principle that the effectiveness of the groundwater extraction is in inverse proportion with the water holding rate S. With the groundwater extraction effectiveness evaluation method of the invention adopted, an extraction method can be provided for the effectiveness of the groundwater extraction of the low-permeability soil layer; parameters involved in the method fully consider the stratum characteristics of a weak soil region and groundwater storage laws; the groundwater extraction effectiveness evaluation method is of great guiding significance for the extraction operation engineering of the low-permeability soil layer, in particular to the restoration engineering of polluted groundwater; and the extraction effectiveness of different soil layers can be compared with each other by means of the effective extraction rate and the effective water holding rate, and therefore, engineering design can be guided.