The existence of space debris has been causing great threats to the security of spacecraft in orbit. Space debris will occupy the limited and precious orbit capacities, so more and more debris generated in the space will also be a huge threat. The real-time high precision orbit determination of debris based on laser ranging technology can effectively avoid the collision between the debris and the spacecraft. In order to make high precision laser ranging to small size space debris, the 53 cm diameter binocular was developed here, which was capable of fast and steady tracking space targets of 400 km above the ground. Combined with low-power high-repetition-rate sub-nanosecond laser generator and single photon detecting technology, the space debris laser ranging technique was implemented on this binocular telescope. According to the laser ranging formulas, the detecting capability of this space debris laser ranging system was researched and analyzed. When the space debris was 1 000 km away from the ground station, the minimum size of the echo photon which can be detected is about 478.5 cm. This space debris laser ranging system has been putting into observation, and the practical observation results indicate this system has the capability to detect meter level debris in ca. 1 000 km distance.