An infrared small target detection algorithm based on the specific target shape template is presented.Firstly，the small target template is gotten through low-pass filter，background subtraction method and high-pass filter.Secondly，a more accurate background image is obtained by using convolution operation of the target template and infrared sequence.Finally，by using background subtraction method，the final infrared small target image is achieved.The computer simulation results show that the presented method has a better performance for the detection of the small infrared target.It’s simple and easy to implement.It achieves a good performance for the improvement of the image quality and the enhancement of Signal to Clutter Ratio （SCR）and SCR gain.