In view of the fact that the existing infrared image enhancement methods suffer from under enhancement, over enhancement and noise amplification, an adaptive weighted histogram equalization method for infrared image enhancement is proposed. In the proposed method, the adaptive weighting coefficient of histogram is put forward, which is inversely proportional to the square root of the histogram frequency corresponding to each gray level, appropriately increases the histogram with smaller frequency, and appropriately suppresses the histogram with larger frequency. After the histogram frequency of each gray level is weighted processed with adaptive weighting coefficient, the weighted histogram is equalized, and finally, the enhanced image is achieved by gray level mapping. Experimental results show that compared with existing methods, the enhanced image by this method has higher contrast, is more rich in edge and detail information, its entropy, average gradient and standard deviation are 0.23, 2.2 and 3.7 higher than those of existing methods, respectively. Therefore, this method outperforms the latest proposed existing methods in image enhancement effect.