The functional near-infrared spectroscopy (fNIRs) is a new convenient non-invasive optical imaging technology to explore human brain activity through cerebral hemodynamics within human brain. However, the fNIRs signal is susceptible to interference induced by human relative motion and physiological activity. The interference can damage the quality of signal, so it is important to develop approaches to eliminate the motion artifact and physiological interference from fNIRs signal. Brief introduction to current development of fNIRs signal processing techniques to correct the signal contaminated by motion artifact and physiological interference is given. The current problems of fNIRs techniques, some promising research fields and the correlation between fNIRs and functional magnetic resonance imaging are discribed. A brief conclusion for fNIRs signal processing techniques is obtained.