To solve the problems such as driving safety and energy consumption existing in tunnel lighting control system, an automatic control system of tunnel lighting is designed based on stepless control method. The tunnel lighting control model is established based on “Specifications for Design of Ventilation and Lighting of Highway Tunnel (China)”. Simulation experiment of tunnel lighting control based on the established stepless control model is completed with Matlab. Compared with theoretical luminance data, simulation results show that the automatic control system can meet the luminance requirements of actual tunnel lighting, the error can be controlled less than 2%. Compared with HPS (high pressure sodium) lamps and LED (light-emitting diode) lamps with the consideration of maximum lighting value, the stepless controlled LED lamps can save more than 80% and 35% energy than HPS lamps and LED lamps respectively, and can save more than 20 % energy than 4-steps controlled LED lamps.