A wristband biosensing system, a wristband biosensing apparatus, and a biological sensing method are provided. The system includes a wristband body worn on a wrist of a user, at least one physiological signal sensor, at least one deformation sensor, and a processing device coupled to the physiological signal sensor and the deformation sensor. The physiological signal sensor is disposed on the wristband body at a position corresponding to at least one sensing portion of the wrist to detect a physiological signal of each sensing portion. The deformation sensor is disposed around each physiological signal sensor to detect deformation of each sensing portion and output a deformation signal. The processing device receives the physiological signal and the deformation signal, inquires a compensation signal corresponding to the deformation signal, and corrects the physiological signal by using the compensation signal, so as to output a corrected physiological signal of each sensing portion.