In the coastal area of Guangdong, slit-less spectra for first return strokes of lightning between the cloud and ground were obtained. After spectrum analysis and line identification were done by using multi-configuration Dirac-Fock (MCDF) method, parameters like wavelengths, oscillator strengths, transition probabilities, and excitation energies were calculated. According to the relative intensities of lines and transition parameters, temperatures for individual lightning strokes and at different heights of the discharge channel were calculated by using multiple-line method. The result shows that the temperatures in return stroke channel varied from stroke to stroke. In general, the more intensive the lightning discharge, the higher the value of channel temperature. On the other hand, for a certain return stroke channel, the temperatures at different positions show signs of falling away with increasing height along the discharge channel. Compared with that of Qinghai plateau, lightning in Guangdong coastal area is more intensive, and the lines from higher excitation potential of N II in these lightning spectra are easier observed.