<p>Effective characterization of early fatigue cracks is crucial for assessing the residual life and failure analysis of metallic components. This study employs electromagnetic ultrasonic mixing technology, which offers advantages such as non-contact measurement and high repeatability, to quantitatively analyze fatigue cracks. We establish an electromagnetic ultrasonic mixing detection system based on the nonlinear wave law, optimizing parameters including exciting frequency. Experiments are conducted on both crack-free and cracked specimens, revealing that the nonlinear modulation phenomenon of mixing waves can indicate the presence of fatigue cracks. We investigate the effects of crack length and depth on the nonlinear modulation, defining a comprehensive mixing nonlinear coefficient to address the differing sensitivities of the sum and difference frequency coefficients. The relationship between this coefficient and crack length is fitted to predict crack length. Our findings demonstrate that the comprehensive mixing nonlinear coefficient effectively characterizes fatigue cracks quantitatively, highlighting the novelty and applicability of this approach.</p>