Abstract: Circuit inductance exists at discharging circuit of transmissionline, it includes the inductance at the main switch of thyratron when conducts, the linking inductance between the linking cables, the matching resistance inductance and the load inductance. When a long pulse is generated by transmissionline, the circuit inductance can be omitted. However, when the pulse is short (such as shorter than 200 ns), especially when ferromagnetic core kicker acts as the load, the effect is obvious. The short pulse current is needed in order to generate long time interval synchronous radiation light pulses by using online assembly of pulse convex orbit and DC convex orbit. This paper analyses the effect and presents several experimental results. It also supposes two practical cases to decrease the