Abstract: A method for detecting the thicknesses of coating layers of nuclear fuel particles, comprising: collecting a surface image of a sample to be tested under a first amplification factor (S310); determining a testable particle in the surface image (S320); collecting a cross section image of the testable particle under a second amplification factor, wherein the second amplification factor is greater than the first amplification factor (S330); and determining the center of the testable particle in the cross section image and profile lines of all coating layers, and determining the thickness of each coating layer according to the center and the profile lines of each coating layer (S340). Also provided is a device for detecting the thicknesses of coating layers of the nuclear fuel particles.