The optical properties and bandgap tunning of InGaN/GaN nanwires were studied. According to the power-dependent and time-resolved PL, we can not observe that the strain-induced piezoelectric field existed in nanowires. Compared with the simulation results, we suggested that the strain released through the defects and interdiffusion effect in nanowires. From temperature dependent PL and TRPL,the few quantum-like localization centers existed in nanowires and the carrier recombination process was dominated by them. Additionally, the external stress is also supplied on the nanowires and the variation of bandgap was dominated by the long-axis of nanowires. The variation of bandgap is decreasing from the center to the top of nanowires and it is also due to the strain distribution in nanowires.