In avionics systems, it is a basic requirement for the avionic data bus to provide efficient and reliable real-time communication for airborne electronic equipment, and the transmission line is an important carrier for transferring data over the avionic data bus. The state transition function, spectral characteristics and attenuation characteristics are obtained by analyzing the structure, the distributed parameter and lumped parameter model of the transmission line. The transmission error caused by signal attenuation during transmission is further analyzed considering the electrical characteristics of the transmission line, and the theoretical numerical model of the relationship between the electrical parameter and the bit error rate is obtained. By using the numerical model deduced from the study, the performance of the ARINC429 bus is studied in detail.Meanwhile, the bit error rates of the transmission lines with different diameters are calculated considering the permitted minimum signal-to-noise ratio in transmission. The results show that even slight changes in the diameter of the transmission line may lead to order-of-magnitude changes in the bit error rate of the data bus.The study provides a reference for selecting the transmission line by means of physical data for the aviation data bus.