This paper proposes a novel circuit-level design in order to enhance the radiation tolerance of an analog switch integrated circuit (IC). After analyzing the mechanisms of single-particle sensitivity in a high-voltage analog switch chip fabricated using a commercial 1-μm complementary metal–oxide–semiconductor (CMOS) process, a diode unit was employed to reduce the VGS (voltage between the gate and the base) of the parasitic triode within the metal–oxide–semiconductor field-effect transistor (MOSFET) of the switch. This reduction lowered the probability of activating the parasitic triode in response to single-event effect (SEE). Subsequently, single-particle irradiation experiments proceeded with the high-voltage analog switch chip, both with and without the diode unit. In the unreinforced device, the current of the power supply reached 100 mA within 11 s of single-particle irradiation at 75.8 MeV•cm2/mg. In contrast, in the reinforced device, the current of the power supply remained relatively stable under irradiation at both 37.2 and 75.8 MeV•cm2/mg. These findings indicate that the reinforced analog switch chip exhibits an SEE tolerance exceeding 75.8 MeV•cm2/mg, highlighting its potential to enhance the radiation tolerance of analog switches.