Automobile antiscratch radar is designed to avoid scratches with the front car. The radar system estimates the cross range between two cars by estimating DOA of the wave reflected by front car. In our radar system, the front car is described by a distributed source model as algorithms based on the assumption of the point source model will seriously deteriorate. We propose an algorithm that estimates the central angle and angular extension of distributed sources in MIMO system unlike most existing algorithms which are on the assumption of point source model. Assuming that the car width is known, we are able to estimate the cross range between two cars. Theoretical analysis and computer simulation show that this method is not only effective but also has good estimation accuracy.