The present invention discloses a brain volumetric measuring method for measuring brain volumetric changes of a subject. The method at least comprises the following steps. First, a light source is provide and emitted into the head of the subject through a light source emitting position. And then, a first optical signal is obtained by receiving numerous scattered photons from the head of the patient through several second positions of. A second optical signal will be obtained by processing the first optical signal. The present invention also discloses a brain volumetric measuring system for performing the abovementioned method.
