In the research of three-dimensional imaging technology, the extraction of image depth is not affected by the illumination direction of the light source and the launch characteristics of the object surface, meanwhile with no shadow, and it can accurately show the three-dimensional depth information of the object surface. We propose a depth acquisition method to obtain the high-quality depth images, using the optimal entropy threshold image segmentation method based on improved genetic algorithm to segment the image and then obtain the depth image. This method can obviously improve the accuracy and real validity of the obtained depth image. The improved genetic algorithm can quickly approximate the optimal threshold, greatly shorten the threshold time of the optimal threshold image segmentation, and improve the accuracy of segmentation efficiency and depth acquisition.