A high voltage pulse Tesla transformer with a coupling coefficient of 0.75 was designed and experimentally investigated. The transformer was employed to charge a spiral water pulse forming line (PFL) in a high current electron beam accelerator, and was featured by its compactness, stability, and reliability. When the primary input voltage is 55 kV, the transformer can charge the PFL to 720 kV with an energy conversion efficiency of 36%. The formulas for calculating the primary and secondary inductances of the transformer were deduced, with which the main parameters of the transformer were calculated theoretically. The distributions for electrical and magnetic fields in the transformer were obtained by the simulations of calculation. In addition, the process of an accelerator of the transformer charging a spiral PFL was simulated through the Pspice software to get the waveform of charging voltage, the diode voltage, and diode current of accelerator. The theoretical and simulated results agree with the experimental results.