The invention relates to the composition, structure characteristics and preparation method of a new type of aluminum-titanium-carbon master alloy grain refiner and its application to aluminum and aluminum alloy grain refinement methods and effects. The present invention proposes a composition of an aluminum-titanium-carbon master alloy refiner prepared under the action of an ultrasonic field, which is characterized in that the main component of this type of refiner only needs to include aluminum (Al) , Titanium (Ti), carbon (C) without the need for other additional components. The method for preparing an aluminum-titanium-carbon master alloy under the action of an ultrasonic field proposed by the present invention is characterized in that raw materials such as pure aluminum ingot, potassium fluorotitanate, and graphite carbon are prepared according to the pre-designed master alloy composition; The aluminum ingot is melted by internal heating, and then various raw materials are added; ultrasonic waves are added to the melt that starts to react; after the reaction is completed, the temperature is raised, kept warm, left still, and slag is removed, and then cast into ingots or continuously cast and rolled into wire rods, thereby Get the required master alloy refiner with various components and shapes.