The aim to distinguish infrared objects and natural background can be achieved by calculating the fractal parameters of infrared image.This article computes the new multi-scales DK (MMK) that based on overall performance of multi-scales fractal parameters.Then presents a new target detection algorithm (MKD) that combines MMK and fractal dimension DΔr computed by gray method.As for infrared image,it has been proved that the detection effect of this article′s target detection algorithm is better than the previous methods based on fractal theory.