The study of III-V semiconductor nanowires has become a popular field of multidisciplinary research, for they have significant potential in exploring new physics and propelling novel electronical and optical applications. To understand the quantum structure and carrier dynamics, as well as to seek ways to improve the performance of nanowire-based devices, charaterisation is needed to study plenty of nanowires, for the nanowires' inhomogeneity due to bottom-up growth approach. Here I present an efficient, non-destructive characterisation method for III-V nanowire study, which based on Micro-photoluminescence spectroscopy. In this thesis, I described the related theoretical models and the experimental methods, and presented results of nanowire samples studied via this characterisation method. Samples include Zn doped GaAs nanowires and GaAs nanowires with quantum confined heterostructures such as dot-in-wire structures, quantum well core-shell nanowires, and multiple-quantum-well nanolasers. Using this method, parameters of nanowires were calculated, and correlations between parameters were determined.