An exercise physiological sensing system, a motion artifact suppression processing method and a motion artifact suppression processing device for obtaining a stable exercise heart rate signal of a user during exercise are provided. The exercise physiological sensing system includes a bone conduction object, a signal-to-noise ratio analysis module, and a computation module. The bone conduction object has a physiological sensor. The physiological sensor detects a physiological signal of otic bones of the user. The signal-to-noise ratio analysis module is coupled to the physiological sensor and detects a stability of the physiological signal of the otic bones. The computation module is coupled to the signal-to-noise ratio analysis module and generates the stable exercise heart rate signal according to the physiological signal of the otic bones. Accordingly, the exercise physiological sensing system can effectively improve the detected stability of an exercise physiological signal.