Aiming at the problem of low detection rate of infrared small target in complex background，an target detection algorithm based on Improved High Boost Filtering (IHBF) and weighted local contrast is proposed. Firstly，the infrared image is processed by IHBF operation to suppress most background clutter and extract candidate pixels of the target. Then，the local contrast is calculated by using the gray difference ratio between the target region and the background region. At the same time，according to the dissimilarity between the target and the background，a weighted function is designed to further improve the contrast between the target and the background. Finally，the target is extracted by adaptive threshold segmentation. Experimental results show that the proposed algorithm has excellent detection performance in a variety of complex scenes.