An infrared dim small target detection algorithm based on structural feature convolution neural network(SCNN) is proposed. By introducing the structural features of infrared dim small target into CNN,the pooling layer of CNN is removed,the convolution expansibility is changed,and the layered fusion mechanism is added to overcome the problems that CNN will lose the information of dim small target itself and cannot detect dim small target. The experimental results show that the proposed method has higher detection rate and stronger robustness for different scenes.