The coupling coordination degree (CCD) is considered to be an important yardstick for guiding practice toward sustainable development. It helps quantitatively investigate the interactions between two or more subsystems within a complex system. However, the existing CCD models have inherent shortcomings. Currently, no consensus has been reached on CCD models. In line with this background, this research proposes a new CCD model from the perspective of the cosine of the high-dimensional spatial angle and develops a novel Excel© tool named Ex-CCD. Taking the coupling coordination analysis between economic-social development, resource consumption, and environmental pollution in China during 2000–2016 as an example, a case demonstration is conducted, and the results show that the model proposed in this research can more accurately describe the coupling coordination state of a system. This new model provides a significant theoretical and practical basis as well as a novel perspective for further coupling coordination research.