Distance has a profound impact on all walks of life in modern times, such as autonomous driving's judgment of the distance between front and rear vehicles in traffic; industrial intelligent robots need to know the distance to move objects, and they all need to use cheap and easy-to-obtain sensors. A camera is a good choice, but using a single camera to measure distance can easily lead to misjudgment in complex environments, and dazzling lights can make it impossible to measure distance using a binocular camera. Therefore, triocular distance measurement has been studied. Trying to solve these problems, this paper will introduce the ranging method that has been published in the past, then discuss the basic theory of binocular ranging and illustrate its advantages and disadvantages in practice, and theoretically propose a method using three cameras After ranging methods, discuss the accuracy, practicality, etc. of the two and analyze their advantages and disadvantages.