We focus in this paper the temperature variation effects on the current - voltage ( I-V) characteristics of n-GaN schottky diode. The diode was doped with carrier concentration 1*10(13) cm(-3) and Pt electrode was used. The simulated current were obtained at temperatures from 50K to 500K and voltage up to 2Volt. We use the Srh (Schokley read hall), Cvt (Lombardi Model), Auger (Auger), Fermi (Fermi Dirac), Impact, Bgn (Bandgap Narrowing), Complete ioniz model to get the schottky rectifying current - voltage (I-V) characteristics.. We find that by increasing the temperature from 50K to 500K, the forward schottky rectifying current decreases from 2.7187 Amp to 0.383 Amp. while the forward turn - on voltage decreases. In reverse bias at low temperature the current is high and we increase the temperature the current decreases. The breakdown voltage decreases at higher temperature.