The invention provides a method for preparing a soil conditioner through acarbose fermented waste residues. Specifically, the acarbose fermented waste residues are processed through the preprocessingstep by reasonably controlling the anaerobic reaction condition. The experimental result shows that through the method provided by the invention, the anaerobic treatment time can be remarkably shortened, in addition, the removal rate of drug residues in the waste residues reaches 90% or above, and the removal rate of solid matter reaches 70% or above. The invention further provides a method for making dehydrated and dried solid residues subjected to multi-stage anaerobic treatment into a soil conditioner.