The invention relates to a recycled aggregate special mortar preparation method and relates to the field of building materials. The method includes the steps: using building wastes such as waste concrete, waste bricks and waste lime-sand mortar which are smaller than 690mm in length as raw materials, determining the quantity of the raw materials as required, crushing and drying to enable moisture to be not more than 0.5% prior to gradational sieving, removing metal, wood dust, plastics and sundries during gradational sieving so that recycled aggregates with the grain sizes of 0.075-0.15mm, 0.15-0.3mm and 0.3-0.6mm are prepared, and using the recycled aggregates to prepare special mortar series including putty for interior and exterior walls, high-hardness and washable putty for interior walls, anti-cracking impermeable elastic putty for exterior walls, dry powder ceramic simulating coating putty, high-hardness washable paste putty, interior wall polishing putty, anti-cracking putty for exterior walls, exterior wall ceramic tile cementing agents, gypsum jointing agents, ceramic tile cementing agents, vetrified tile and mosaic tile cementing agents, marble and thermal-insulation board cementing agents, external thermal insulation cementing mortar and polyphenyl particle rubber powder composite thermal mortar. The recycled aggregate special mortar is used as building raw materials. By the recycled aggregate special mortar preparation method, natural resources are protected, wastes are turned to wealth, labor and time are saved, cost is low, and the requirements of low-carbon production and low-carbon life are met.