In the Ohmic contacts of LED electrodes,carriers have different transmission mechanisms between metal electrode and semiconductor. By simulating transferring mechanism of carriers in metalsemiconductor interface,the impact of the interfacial layer and barrier potential on series resistance and leakage current of LED is discussed. Resistance of interfacial layer can be ignored comparing with LED's series resistance because it is very small. With the aging of the LED,the interfacial layer and defects can result in very serious leakage current,let reliability and stability come down,and also provide the theory basis to the LED invalid mechanism.