The channel plasma characteristics of an artificially triggered lightning in Guangdong, China, were analyzed using slit-free spectroscopy technology. Spectral diagnostics were performed to obtain the peak currents by about 30.9 kA (maximum) and 25.6 kA (minimum), which were subsequently simulated using the Modified Transmission Line model with Linear current decay (MTLL). To investigate the electric field distribution, the Finite-Difference Time-Domain (FDTD) method and Transmission Line (TL) model were employed. At a distance of 58 m, the TL-predicted radiation electric field deviates from experimental electric field when assuming a return stroke velocity of 1.3×10⁸m/s, but becomes close alignment with the FDTD-simulation of vertical electric fields. Moreover, the analysis of magnetic fields at 58 m, 90 m, and 1.6 km were compared using FDTD simulations, Dipole approximations, and Charge Magnetic Field Limit (CMFL) estimations. The discrepancies between calculated and experimental values are appeared at 58 m and 90 m, probably due to the near-field interference and measurement limitation. However, they become small at 1.6 km.This work is helpful for the study of lightning electromagnetic field properties and spectral diagnosis.