In the long-range Modulating Retro-Reflector (MRR) communication system, the retro-reflective signal is weak and difficult to be detected. In this manuscript, a novel detection mode of MRR communication based on speckle technology is proposed, which can detect small fluctuation of the light from the modulator. The novel detection mode is simple, modular, inexpensive and suitable for low speed MRR communication. System design as well as the detection principle is descripted. The experiment part was completed the transmission of 1.3 kHz digital signal on 60m distance and analog voice transmission on 330 m distance.