The invention relates to a regeneration method of casting wet type mixed old sand. The regeneration method comprises the following steps: preprocessing casting wet type mixed old sand; wiping with water; drying; preheating; roasting; and post-processing. In the invention, components, such as bentonite, coal dust and ashes, in wet type old sand are effectively removed by a water wiping process, and a residual resin film in mixed old sand is thoroughly decomposed by a roasting process. The regeneration cost is low, and the regeneration effect is great. Actual production and verification show that the performance indexes of regenerated sand reach or surpass those of new sand. The regeneration method is successively applied to the core making production of cold boxes and has remarkable economical and social benefits.