This paper presents dimming control system for automotive 35[W] metal halide discharge(MHD) lamp electronic ballast using digital control method. HID system has been becoming increasingly popular due to its superior performance(high luminous efficacy, good color rendering and long life etc.)over the conventional halogen system. However, this lamp demands a highly efficient ballast and very complex control circuitry that can control complex transient state in applying to automotive. Therefore, in this paper, digital control method for the HID lamp ballast is presented for optimal control that can adapt complex transient state, steady state and various environments. In developed dimming system, the system is designed to control the lamp output voltage step by step using microcontroller according to cds sensor. Therefore the designed dimming control system give good driving condition to diver and realize the power control effectively. The results of the proposed system is verified through various simulation results and the experiment results.