In order to rapidly evaluate and screen G4 lamp with light-emitting diodes (LED) light source (LED G4), the photoelectric performance of LED G4 lamp is studied. Using the integrating sphere, variations of the performance parameters such as luminous flux, luminous efficiency, color temperature with input voltages of drive circuit changing from 10 V to 34.5 V are tested and analyzed in both initial and steady states. The results show that luminous flux and color temperature of tested lamp increase with the raise of input voltage of drive circuit in both initial and steady states, but luminous efficiency tends to decrease. In initial state and steady state, the luminous flux increases as much as 91.40% and 39.34%, and luminous efficiency decreases by 24.3% and 28.1%, respectively. Furthermore, the highest temperature of the center over the tested lamp is tested by thermal imager. The temperature increases with the increase of input voltage of drive circuit. The difference between its start value and end value reaches 40 ℃. Experimental results show that excessive input voltage of drive circuit is not suitable for high performance of LED G4 lamp and temperature rise has a negative impact on its performance. Therefore, we should choose appropriate operating voltage and improve the performance of heat dissipation in practice.