Resistance-reducing with slurry is a key technique in the construction of long-distance pipe jacking. The thickness of the slurry is closely related to the engineering quality.Based on the basic principle of impact image method, a rapid detection method for accurately grasping the distribution condition of slurry outside the pipe jacking is proposed in this article, and the validity of the detection method is explored through model test and field test.According to the results of model test, the normalized impact response intensity is taken as the evaluation index to reflect the distribution condition of slurry. Finally, it has been successfully applied to a large-scale water diversion project in Suzhou. The research shows that the impact image method has obvious advantages over the traditional pressure observation method in detecting the thickness of slurry, which effectively improves the efficiency of detection and the identification ability of high resistance zone. At the same time, the construction cost can be greatly saved by replenishing the weak area of slurry precisely. This method can be popularized for similar projects.