The disclosed light modulator for halogen lamp based on European assembly bus comprises: a bus coupling unit with 68HC08 as MPU to communicate with bus and receive modulating message to modulate lamp reference voltage, and an application module with a power factor correction loop and a voltage modulation loop to adjust lamp average voltage by PWM according to the reference voltage for brightness control. Compared with prior art, this invention is simple and reliable, and can improve factor coefficient by PFC loop.