A smart watch comprises a watch head and a watch strap. The watch head comprises: a first electrode for contacting skin of a watch-wearing wrist; a second electrode for contacting skin of a non-watch-wearing wrist, wherein both the first electrode and the second electrode are electrically connected with a main control unit of the smart watch, so that the main control unit calculates an electrocardiogram according to bioelectric signals detected by the first electrode and the second electrode; and an air bag for contacting the skin of the watch-wearing wrist, wherein the air bag is respectively connected with an air pump and a pressure sensor, and the pressure sensor is connected with the main control unit, so that the main control unit calculates blood pressure according to a detection signal of the pressure sensor.