The present invention refers to a device (1) and a method of measuring a parameter of blood, preferably correlated to the presence or concentration of oxygen in blood. The invention provides to: excite a photosensitive element (18′) in contact with blood by excitation pulses, detect light responses of the photosensitive element corresponding to the excitation pulses, and analyze the plurality of luminescence decay curves at least two time windows (t1-tN). Moreover, the invention provides to: detect one or more light answer analog information regarding the luminescence curve decay at each time window, convert the analog information into digital data, process the digital data and the actual temperature value of blood by taking into account a plurality of data of previous measures of the parameter of blood performed during a previous training, and determine, as a result of the processing step, at least one value of said parameter of blood.