A blood pressure calculation method applied to a blood pressure measurement device comprising a pressurizing motor unit and at least one exhaust valve unit (17,18) in communication with an airbag unit, and the blood pressure calculation method comprising: controlling the pressurizing motor unit to pressurize the airbag unit; measuring pressurized measurement data from the airbag unit during a pressurization process; controlling the pressurizing motor unit to stop pressurizing the airbag unit, and then controlling the at least one exhaust valve unit (17,18) to depressurize the airbag unit; measuring depressurized measurement data from the airbag unit during a depressurization process; characterised in that the pressurized measurement data and the depressurized measurement data are processed to extract or deduce a systolic pressure value and a diastolic pressure value of a blood pressure measurement result;, thus extracting at least one blood pressure parameter from each of the pressurized measurement data and the depressurized measurement data, wherein the blood pressure parameter comprises amplitude data of a sequence of pulse signals and pressure data corresponding to the amplitude data; and wherein the blood pressure calculation method further comprises extracting maximum amplitude data in pressurized measurement and maximum amplitude data in depressurized measurement from the pressurized measurement data and the depressurized measurement data, respectively; calculating an average of the maximum amplitude data in pressurized measurement and the maximum amplitude data in depressurized measurement; calculating a product of the average and a threshold parameter of the systolic pressure in depressurized measurement, and using the calculated production as an amplitude threshold of systolic pressure in depressurized measurement; and extracting or deducing pressure data from the depressurized measurement data based on the amplitude threshold of systolic pressure in depressurized measurement, and using the pressure data as the systolic pressure value of the blood pressure measurement result. controlling the pressurizing motor unit to pressurize the airbag unit; measuring pressurized measurement data from the airbag unit during a pressurization process; controlling the pressurizing motor unit to stop pressurizing the airbag unit, and then controlling the at least one exhaust valve unit (17,18) to depressurize the airbag unit; measuring depressurized measurement data from the airbag unit during a depressurization process; characterised in that the pressurized measurement data and the depressurized measurement data are processed to extract or deduce a systolic pressure value and a diastolic pressure value of a blood pressure measurement result;, thus extracting at least one blood pressure parameter from each of the pressurized measurement data and the depressurized measurement data, wherein the blood pressure parameter comprises amplitude data of a sequence of pulse signals and pressure data corresponding to the amplitude data; and wherein the blood pressure calculation method further comprises extracting maximum amplitude data in pressurized measurement and maximum amplitude data in depressurized measurement from the pressurized measurement data and the depressurized measurement data, respectively; calculating an average of the maximum amplitude data in pressurized measurement and the maximum amplitude data in depressurized measurement; calculating a product of the average and a threshold parameter of the systolic pressure in depressurized measurement, and using the calculated production as an amplitude threshold of systolic pressure in depressurized measurement; and extracting or deducing pressure data from the depressurized measurement data based on the amplitude threshold of systolic pressure in depressurized measurement, and using the pressure data as the systolic pressure value of the blood pressure measurement result.