The invention discloses a method for preparing a one-step molding organic silicon self-adhesive pressure sensitive adhesive. The method is characterized by comprising the following steps: firstly, preparing materials by the following compositions according to the parts by weight: methyl vinyl silicone rubber:white carbon black:silicon micropowder:hydroxyl silicon oil:pressure sensitive adhesive resin:methyl silicone oil=(10-90) parts:(1-50) parts:(10-50) parts:(0.1-3) parts:(4-40) parts:(10-90) parts; secondly, adding the compositions into a reactor which is provided with a stainless steel stirring paddle, a motor and a heating system; thirdly, mixing the methyl vinyl silicone rubber, the pressure sensitive adhesive resin and the methyl silicone oil at normal temperature to be heated to banburying for 1 to 3 hours; finally, pumping for 0.5 to 2 hours, and discharging. The method has the advantages of simple process, environmental protection, wide production application and the like.