For the channel-filter arithmetic in the serial-frame detection ofweak and small infrared targets, the article comments a method of movable channel-filter. That method has resolved the problem resulted from the noise on the edge of the channel. The article also applies Karlman channel-filter to the forecast of the center of the channel. It was confirmed that the method can imp rove the p recise of detection, minimize the size of the channel, and imp rove the ability of anti-noise, calculation speed and precise.