Aiming at disadvantages of all kinds of current ranging methods,a new ranging method based on similarity principle was put forward by using two cameras.We introduced principle of this method,and deduced ranging formula.But the formula can’t be applied to engineering practice directly.In order to overcome the difficulty,we proposed an experimental method which could realize the engineering value of this new ranging method.In order to verify the practicability of this method,two grope of experiments have been done.The results show that the ranging method can measure distance accurately at short or middle distance.Compared with other ranging methods,this method is low-cost and suitable for the visual ranging system of mobile robots.Moreover,it can make the mobile robot get ability of telescope and wide-angle lens at the same time.