Disclosed is a spontaneous exercise electrocardiogram system, adapted to synchronously record and analyze a user to obtain a spontaneous exercise electrocardiogram. The system comprises a electrocardiogram device and a analyzing computer. The electrocardiogram device comprises: an electrocardiogram sensor and a 3-dimensional acceleration sensor for detecting the users electrocardiogram signals and acceleration signals, respectively. Upon the analyzing computer receives the information from the electrocardiogram device, an indicator of physical activity (PA) or new physical activity (NPA) can be determined. After the heart rate of electrocardiogram and heart rate variability being matched and analyzed, the users spontaneous exercise electrocardiogram can be established.
