The invention discloses an oil tea fruit shell powder adding agent and a preparing method and application therefore, and relates to an adhesive adding agent and a preparing method and application thereof. The problem that existing aldehyde adhesive difficultly glues a straw-based panel effectively, and panel sticking exists in isocyanate adhesive is solved. The adding agent comprises modified oil tea fruit shell powder and modified nano-montmorillonite. The method comprises the steps of firstly, preparing of modified oil tea fruit shell powder; secondly, preparing of the modified nano-montmorillonite and thirdly, preparing of the oil tea fruit shell powder adding agent. The modified oil tea fruit shell powder obtained through the method is added into the adhesive, the straw-based panel is bonded, the gluing strength and water resistance are improved, and the agent is used for the field of the straw-based panel adhesive adding agent.