Performance characteristics of self-excited pulsed MHD power systems are investigated with one-dimensional time-dependent calculations using a gas-liquid two-fluid model. First, the Russian pulsed MHD power system "Pamir-3U" is analyzed. The result of numerical simulations of hot-fire tests shows good agreement with the experimental data, confirming the validity of the mathematical model. Performance analysis of Pamir-3U reveals that the power output is approximately constant with the variation of load resistance, while the ballast resistor consumes a large amount of electric power. It is also shown that the system has been optimally designed to supply a large load current. Next, a new system yielding larger power output is proposed and analyzed. The obtained characteristics show that the new system can provide the maximum power output of 25 MW which is 10 MW larger than that of Pamir-3U. (C) 2000 Scripta Technica.