The various states changing with voltage of the luminous flux and efficiency at initial and steady states of a 3.5 W and 6500 K AC LED light source are mainly researched under different voltages. Researches show that the current, luminous flux and power of AC LED light source at initial and steady states all rise with the voltage rising from 205 V to 235 V. And the current and the luminous flux at initial state increase to 79.3% and 75.3% respectively. The current and luminous flux at steady state increase to 80.28% and 45.93% respectively. However, the luminous efficiency at initial state and steady state drops along with voltage rising, the luminous efficiency of initial state and steady state drop to 18.67% and 33.22% respectively. After the lights up, the highest temperature of AC LED light source at steady state rises along with the voltage rising, and the highest temperature rises to 91.80%. Results show that the photoelectric performances of AC LED light source are directly affected by the changing voltage.