To obtain the optimal luminaire-distribution parameters (LDPs) of highway tunnel threshold and tran- sition zone lighting system with symmetrical luminaire-distribution-style (LDS), a parameter optimization model (POM) of SLDS for tunnel threshold and transition zone was established, by taking illuminance of road surface meeting lighting requirement as constraint conditions, and taking minimum total power consumption of the light- ing system as the objective function. In this paper, Yanlieshan tunnel of Jiujing highway was taken as an exam- ple for the optimization. The optimal LDPs and the corresponding total power of the lighting system were ob- tained by the POM, and a comparison analysis between the optimization results and that of the real tunnel light- ing system was performed. The research results show that the total power of the LED lighting system installed according to the optimized LDPs was less 69.59% than the total power of the transformed lighting system in- stalled with electromagnetic induction?lamps. A simulation experiment of the optimized LDPs of Yanlieshan tun- nel lighting system was carried out by using Dialux software and the simulation results verified the correctness of the POM. The comparison between the optimized brightness adaptation curve and the theoretical brightness adaptation curve of the highway tunnel indicates that the optimized LDS can meet the visual adaptation require- ment preferably.