To study the attenuation characteristics of signal transmission in low voltage distribution network is very important to optimize the stability and reliability of the physical layer of signal transmission in the local communication system. This paper measures signal transmission attenuation influenced by cross-sectional area, length and network structure of low voltage power line, calculates and analyzes the amplitude frequency attenuation characteristics change with the basic properties of power line within the range of wide band accurately. The little distance and normal T type network structure models are proposed to research the frequency selective fading caused by multipath transmission of power line communication channels. Simulation and measurement statistics results of signal transmission attenuation characteristics influenced by basic characteristics are showed by diagrams intuitively. Those results are very useful for understanding and grasping the essential reasons of low voltage power line transmission characteristics, which provides an effective analysis method for the prediction of signal transmission characteristics in complex distribution network. This work is supported by Science and Technology Project of State Grid Corporation of China “Research on Power Utilization Information Acquisition System and Monitoring & Diagnosis Optimization Techniques for Equipment Performance”, China Postdoctoral Science Foundation (No. 2015T80961), and Natural Science Foundation of Chongqing (No. cstc2016jcyjA0214).