The present disclosure relates to a device, method and system (100) for calculating, estimating, or monitoring the physiological parameters of a subject. At least one processor, when executing instructions, may perform one or more of the following operations: receiving a first signal representing a pulse wave relating to heart activity of a subject, receiving a plurality of second signals representing time-varying information on the pulse wave, determining a blood oxygen level of the subject based on the plurality of second signals, identifying a first feature in the first signal, identifying a second feature in one of the plurality of second signals, computing a pulse transit time based on a difference between the first feature and the second feature, calculating a blood pressure of the subject based on the pulse transit time.
