The invention discloses a system for generating high-stability high voltage, which belongs to the technical field of a high-voltage generator. A circuit structure of the system comprises a switch conversion circuit, a high-ratio transformer, a voltage multiplier, a feedback sampling circuit and a frequency-adjustable PWM control circuit, wherein the transformer is provided with a primary side and a secondary side; and the primary side is connected to a high-frequency wave output end of the switch conversion circuit, and is a series-parallel resonant circuit consisting of a resonant inductor Ls, a resonant capacitor Cs and an equivalent parallel resonant capacitor Cp of the high-ratio transformer. The system reduces the adverse impact of parasitic parameters of the transformer, improves the high-frequency operating frequency of the circuit, reduces the voltage drop of the pulsation and load of an output voltage, strengthens the stability of the output high voltage obviously, realizes a soft-switch operating mode by adjusting circuit operating points, further strengthens the stability of the output high voltage, improves operating frequency, reduces the volume of magnetic elements, and reduces the occupied space of the system obviously.