An active reflector is one of the key technologies for constructing large telescopes, especially for millimeter/sub-millimeter radio telescopes. This article introduces a new efficient laser angle metrology system for an active reflector antenna on large radio telescopes. Our experiments concentrate on developing an active reflector for improving the detection precisions and the maintenance of the surface shape in real time on the 65-meter prototype radio telescope constructed by Nanjing Institute of Astronomical Optics and Technology (NIAOT; http://65m.shao.cas.cn/). The test results indicate that the accuracy of the surface shape segmentation and maintenance has the dimensions of microns, and the time- response can be on the order of minutes. Our efforts proved to be workable for sub- millimeter radio telescopes.