Arcjet thruster has been a widely used electrical propulsion technology on GEO satellites since 1993. In its long history of technical development and commercial application, lifetime verification of an arcjet thruster is always one of the most important and expensive tasks. Considering that the main life limitation of an arcjet thruster is electrode ablation and a significant share of the total ablation happens in its starting-up process, the starting-up process is studied with arc voltage signals. Through interpretation of arc voltage signals, the transfer process of the arc root on the anode surface is identified, and△T (the duration of the arc root transfer process) is suggested to be a characteristic parameter for fast evaluation of lifetime assessment and design optimization for an arcjet thruster. With this criterion, the influences of typical parameters on the starting-up process are established through comparison with a benchmark parameter. According to experimen-tal results, an increase of the gas flow will obviously reduce △T, while a smaller swirl aperture and a longer throat channel do not have a remarkable correlation with △T. Moreover, with a sample of a smaller throat diameter to increase the flow velocity, a reduction of △T is achieved. Meanwhile, the modifications also affect the stability of arcjet thruster operation, which is also discussed.