In the recent years，more and more light-emitting diodes use indium tin oxide (ITO) as the current spreading layer. But if there is not any treatment, the electrical properties of light emitting diode are very poor. So to get excellent electrical properties of light emitting diode, annealing is an effective method to improve the electrical properties of light emitting diode using indium tin oxide as the current spreading layer. However, the annealing time and temperature can affect the electrical property of light emitting diode individually. In order to investigate this problem，we measured the series resistance and ideality factor of the light emitting diode got under different annealing time and annealing temperature. According to the model proposed by Jay M. Shah，we can inferred the characteristics of indium tin oxide and P-type GaN contact. The results showed that: the electrical properties of the light-emitting diode can reach an excellent value with increasing annealing temperature and time, and if continuing to increase in temperature or time, it can lead to a decline in light-emitting diode electrical properties. It is very helpful to optimize the annealing temperature and time and manufacture excellent electrical properties of devices.