By utilizing the 3D finite-difference time-domain technique, the influence of the photonic crystals with various structure parameters on the light extraction efficiency of light-emitting diode (LED) are studied. Based on the near to far field transformation, the far field radiation characteristics of PhC LEDs for two types of defect with different hole size are investigated. It is found that the light extraction efficiency and energy directionality in the far field radiation can be improved by incorporating defect into the PhCs and decreasing the hole size near to the defect.