Front vehicle ranging plays a vital role in the field of autonomous vehicle technology. Aiming at the problem that the current vehicle ranging technology based on monocular vision neglects the lower edge of the vehicle connected to the ground, this paper proposes a monocular vision ranging model based on vehicle lower edge estimation and inverse perspective transformation, which realizes high- precision distance measurement of lateral and longitudinal directions of vehicles in front. Firstly, the vehicle's key point estimation and geometric relationship model are used to estimate the lower edge of the vehicle, then the distance measurement key points are calculated, and the point-based inverse perspective transformation distance measurement model is used to calculate the distance. The experimental results show that, compared with other monocular vision vehicle ranging algorithms, this method improves the accuracy and stability of ranging.