Abstract: The fast rising pulse source with double exponential waveform can be produced in Marx circuits based on avalanche transistors.To find the influence between the circuit parameters and pulse,built equivalent circuit about the discharge loop，simulated the problem by the Pspice program,experiment verified the result by a pulser with threestage Marx circuit.The result was that the charge voltage,the capacity,and the load resistance mainly influenced the peak value and the pulsewidth of the pulse.The peak value and pulsewidth would be lager when the charge voltage and the capacity were bigger. The load resistance affect pulsewidth also，and pulsewidth would be lager when load resistance is bigger.