Abstract: The FIR digital filter is widely used in many fields which require the signal path with linear phase,such as image procession,data transmission,and so on.The filter performance can be easily changed with the varying filter parameters.This article elaborates the designing thought of digital filter,and discusses the linear phase condition and margin characteristic of FIR.And then,it sets the rectangle window and Blackman window as examples,realizes the filter’s simulation design by means of MATLAB.The simulation result showed that the procedure was simple and easy to be achieved when designing digital filter with the help of computer software,and all the filtering norms could reach the assigned claim.It may promote the digital filter’s application.

Key words: digital filter, MATLAB, FIR, window function