A 3-way solenoid valve (20) is arranged between a cuff (10) and a first pressure sensor (30), wherein the common port of the 3-way solenoid valve (20) is connected with the first pressure sensor (30), the normally open port thereof connected with the cuff (10), and the normally closed port thereof connected with the air atmosphere during zeroing process. Moreover, an independent timing circuit (45) is provided additionally. In the measurement method of the present invention, the zeroing is performed with the help of the 3-way solenoid valve (20). Once a state of overtime or overpressure occurs, an air pump (50) is immediately closed, and a quick-deflation solenoid valve (60) is opened so that the pressure in the cuff (10) is released to ensure safe application.