The speech signal processing is the cross-discipline which combines the voice science with the digital signal processing technology. The voice is taken as a special signal, i.e. a complex vector. By using the command functions in the digital signal processing tool－MATLAB, the digital signal processing can solve many problems. The spectrum of voice signals are analyzed, which is the same as the spectrum analysis of common signals. A variety of digital filters (FIR low-pass filters, high pass filters, band-pass filter and IIR band stop filter) are used to filter and analyze the voice, and the voice signals are compared with the original signal. Finally, the conclusion is drawn.