Conventional electromagnetic (EM) absorbing materials exhibit fixed EM properties, limiting their ability to adapt to spatiotemporal variations in the ambient EM environment. With the advancement of high-resolution radar imaging systems such as synthetic aperture radar (SAR), the EM reflection differences between targets and their surroundings can be precisely identified, significantly increasing the risk of target exposure. To achieve effective camouflage under imaging conditions, it is imperative to develop dynamically tunable EM absorbing materials operating in the microwave band that can modulate their EM responses to match the environment, thereby reducing detectability. Recent progress in novel material and device systems, as well as deformation-driven modulation mechanisms, has enabled the realization of broadband EM absorption with large modulation depth. This review summarizes research advances in representative material systems including graphene, diodes, and fluidic media, alongside mechanical deformation-based modulation approaches. The EM modulation mechanisms of various technologies are analyzed, and design strategies for extending modulation bandwidth and enhancing modulation depth are discussed. Finally, future development directions of dynamically tunable EM absorbing materials are proposed.