In the interest of realizing carrier communication using LVPL, it is sticking point to analyse and design the coupling circuit of the communication. Higher efficiency of loading carrier signals is necessary. On the other hand, disturbs from LVPL should be overcome. Penman commendably resolved the difficult problem with the "complex-coupling-technology" of combining " electromagnetism - coupling" to "RC-coupling". Based on the " complex - coupling-technology" , "the interface circuit of the communication is analyzed and designed with LVPL. Simulation results and experimentation results show : the coupling circuit not only has higher efficiency of loading carrier signals but also can completely close off 50 Hz signal from LVPL. Therefore, the coupling circuit can apply to communication systems on LVPL.