Functional near-infrared spectroscopy (fNIRS) is a non-invasive methods for acquiring neuronal activation coupled hemodynamic changes from the brain evoked by some particular stimuli. Recently, the study of fNIRS for implementation of brain-computer interface (BCI), for the acquisition and decoding of hemodynamic signals in the brain. In order to generate neuronal signals, arithmetic tasks were administered to eight subjects. This paper proposes an independent component analysis (ICA) to extract hemodynamic signals and unwanted signals. Significantly, the clearer hemodynamic response has been found after restoring the independent components from ICA which is indicated by increasing the t-value.