In the detection of pavement cracks, the traditional manual detection method is low in accuracy and efficiency, and the monocular vision technology can not accurately obtain the depth information, only two-dimensional plane information. Based on this, binocular line structured light technology is introduced in this paper, and a 3D crack extraction algorithm based on the average ground height is proposed to realize the 3D crack information acquisition. The algorithm extracts the lowest point of each column of pixel values as the starting point, diffuses to the left and right to form an edge extraction range, calculates the average value of pixels outside the extraction range of the column edge as the ground average height value, and then starts to traverse each pixel value with the lowest point as the center. When the left and right pixels exceed the ground average height value, two pixels are determined as crack edges. All columns are integrated to achieve the extraction of the entire crack edge. The experimental results show that the proposed crack identification algorithm can extract the crack edge more accurately. Compared with the Canny edge extraction algorithm, the data show that the algorithm in this paper performs better in continuity. The horizontal correlation data of the algorithm in this paper are generally higher than that of the Canny edge extraction algorithm, with an average increase of 30%.