The present disclosure discloses a device, system and method for testing cardiac exercise functions. Chronotropic Competence Indices (CCIs) are proposed to quantitatively describe the adaptation capability of cardiopulmonary system in response to exercise intensity variation in terms of heart rate changes, and thereby describes the dynamic process of the heart in the body metabolic process. The present disclosure discloses a device which measures the CCIs in real time by using the wearable technology, and referred to as Cardiac Exercise Test (CET). Compared with the Cardiopulmonary Exercise Testing (CPX) and parameters measured by the CPX such as a maximum oxygen uptake, the CCIs have clear clinical meanings and specific normal reference values； and the CET reduces the risk of the test. It is simple to use, and can be used anytime anywhere. It is of great importance in wide clinical applications, and is of great significance in prevention and rehabilitation of cardiopulmonary disease.
