In our experiments,the PL spectra of several In x Ga 1 x N alloy samples with In contents x=0.1,0.15 and 0.25 were measured as a function of temperature ranging from 10 K to 300 K.S-shaped temperature dependencies were observed in all InGaN samples and a sharp decrease in the full width at half maximum occurred with decreasing temperature in the moderate temperature region.It was found that both phenomena are relative to localization effects.In addition,the degree of localization effects in three samples was investigated using the band-tail model.Our findings are presented in this paper. In our experiments, the PL spectra of several In x Ga 1 x N alloy samples with In contents x = 0.1, 0.15 and 0.25 were measured as a function of temperature ranging from 10 K to 300 KS-shaped temperature dependencies were observed in all InGaN samples and a sharp decrease in the full width at half temperature with moderate temperature in the moderate temperature region. It was found that both both are relative to localization effects. In addition, the degree of localization effects in three samples was investigated using the band -tail model.Our findings are presented in this paper.