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The variability characteristics of active galactic nuclei (AGNs) serve as a powerful diagnostic tool for probing the physical mechanisms underlying accretion processes and jet formation in supermassive black holes. Using long-term optical time-domain monitoring data from the Zwicky Transient Facility, this study applies the damped random walk model to fit the light curves of radio-quiet AGNs, enabling the extraction of their optical variability amplitudes and characteristic timescales. We investigate the origins of optical variability in radio-quiet AGNs. The main findings are as follows: (1) There is a significant correlation between variability amplitude and Eddington ratio; in contrast, variability amplitude is not significantly correlated with radio luminosity. These results indicate that the optical variability of radio-quiet AGNs is primarily driven by the Eddington ratio, rather than relativistic jets. (2) The relationship between variability amplitude and Eddington ratio in radio-quiet AGNs is highly dependent on the accretion mode. For the efficient accretion mode, the variability amplitudes of radio-quiet AGNs are inversely correlated with the Eddington ratio; in contrast, for the inefficient accretion mode, these variability amplitudes are positively correlated with the Eddington ratio. (3) A significant correlation between optical variability amplitude and X-ray luminosity is observed for radio-quiet AGNs. This finding may support a scenario in which variations in UV/optical emission and heating of the X-ray corona are jointly regulated by magnetohydrodynamic turbulence within the accretion disk.