The paper presents a complete composite gate turn-off thyristor (GTO) model, which is based on the combination of the p-n-p and n-p-n transistor models. PSpice simulations and parametric sensitive analysis are performed with the complete composite model and calculated results are given, which show that it corresponds statically and dynamically with the practical device. In particular, the GTO gate dynamical characteristics in practical circuits are discussed and experimental results are included.