GaNbased microsized lightemitting diodes (microLED) has gradually become the main light source in many optoelectronic devices such as visible light communications and nextgeneration displays. Low external quantum efficiency (EQE)，caused by nonradiative recombination and quantum confined Stark effect (QCSE)，is the main bottleneck in applications of microLEDs. In this report, the reasons for low EQE of microLEDs are discussed, and the physical characteristics of microLEDs are analyzed and several optimal methods are suggested to improve EQE.