This paper first studies the impacts of extraction and interpolation on signal spectrum in multirate signal processing.Then it theoretically derives the signal spectrum after integer times extraction and integer times zero-value interpolation by using the Fourier Transformation（FT）

obtaining the regular pattern of signal spectrum after extraction and interpolation as well as the method for avoiding spectrum aliasing.In addition

it analyzes it in experimental simulation

verifying the correctness of the theoretical derivation.Finally it presents a few points for attention in multirate signal processing.