The invention discloses a method for preparing a micron-sized particle transmission electron microscope sample, and method comprises the following processes performed in a focused ion beam-scanning electron microscope dual-beam system of selecting sample particles of a micron size order to be measured; applying an ion beam deposition process to deposit a first material on the outer surface of thesample particles to form a protective layer covering the sample particles; welding the sample particles coated with the protective layer to a sample carrier; and applying an ion beam cutting process to cut the sample particles coated with the protective layer to form a test sample with a thickness on the order of nanometers on the sample carrier. The method can simplify the sample preparation process of micron-sized particle transmission electron microscope samples, improve the speed of sample preparation, and improve the success rate of sample preparation.