A linear array infrared push scan sensor has low scanning frame rate and belt noise. Therefore, a small target detection method based on Robinson-Guard filter and pixel convergence is proposed. At the first stage, some sample windows are uniformly placed on the infrared image, so that the sample windows can focus on the high-lighted region according to the brightness gradient of image. Then, the weighted superposition of the sampling window is used as the target probability map, which combines the target energy information, local contrast, target pixel convergence, and other features of the infrared image. Finally, the target is obtained by global threshold segmentation, and the detection of small infrared target is realized. Experimental results show that the method can detect the small and medium size infrared targets and is effectively resistive to the band noise caused by the detector.