In order to improve the detection ability of infrared dim small target in complex environmentby introducing the human visual attention mechanisma weak small target detection algorithm based on difference histogram of oriented gradients coupling saliency mapping is designed. Considering the intensity difference between the real object and its neighborhoodthe DFT was used to calculate the amplitude and phase spectrum of the infrared image for calculating the spectrum residual between themand the saliency mapping was outputed by combinning with Gaussian filtering method to effectively highlight the salient region. The difference between the gradient amplitude and the gradient direction of the target and the background area was analyzedand the difference histogram of oriented gradients of the infrared image was calculated to fully suppress the background clutter and noise. And the fusion feature mapping corresponding to the image was formed by combining saliency mapping and multi-scale difference histogram. Finallythe adaptive threshold segmentation method was introduced to accurately locate the real target from the fusion feature map. Multiple sets of test data show thatcompared with the existing infrared target detection technologythe proposed algorithm can better locate small and weak targetsand have an ideal ROC curve.