Applying series and parallel structure, a high current pulse generator was designed with thyristor. By analyzing the conducting current in circuit, the self triggering principle of the pulse generator is described. The variation of magnetic field in lens excited by output pulse current is simulated. The output characteristics of the circuit were measured. Using capacitors with parameters of 600 V/2200 μF and DC voltage of 550 V, under load resistance of 6 Ω and load inductance of 31.5 MH, a pulse with amplitude of -2.1 kV, FWHM of 7.34 ms, and pulse front of 450 ns was obtained. The pulse current is -225 A in amplitude, 6.3 ms in FWHM, 4.11 ms in pulse front.