Aiming at problems such as low precision

large amount of calculation and poor real-time performance of image feature matching algorithm that used in distance measurement by visual sensor

an improved scale invariant feature transform（ SIFT） image feature matching algorithm is proposed and applied to the binocular distance measurement system. In order to improve the efficiency of the algorithm

the improved SIFT algorithm is based on the simplified scale structure space

which takes Manhattan distance as the similarity measurement in the nearest neighbor query. To eliminate mismatching points

the random sample consensus（ RANSAC） algorithm is used after first match. Based on the second match points with high precision

the pixel information of match points is extracted to calculate distance

and the feasibility of the algorithm is verified by distance measure experiment.Experimental results show that the distance of target with high precision meets the requirements of observation equipment based on the proposed method.