Manipulation of thermal transport (pursuing ultra-high or ultra-low thermal conductivity) is on emerging demands, since heat transfer plays a critical role in enormous practical implications, such as efficient heat dissipation in nano-electronics and heat conduction hindering in solid-state thermoelectrics. It is well established that the thermal transport in semiconductors and insulators (phonons) can be effectively modulated by structure engineering or materials processing. However, almost all the existing approaches involve altering the original atomic structure, which would be frustrated due to either irreversible structure change or limited tunability of thermal conductivity. Motivated by the inherent relationship between phonon behavior and interatomic electrostatic interaction, we comprehensively investigate the effect of external electric field, a widely used gating technique in modern electronics, on the lattice thermal conductivity (). Taking two-dimensional silicon (silicene) as a model system, we demonstrate that, by applying electric field (Ez = 0.5 V/Å) the thermal conductivity of silicene can be reduced to a record low value of ~0.091 W/mK, which is more than two orders of magnitude lower than that without electric field (19.21 W/mK). Fundamental insights are gained from the view of electronic structures. With electric field applied, due to the screened potential resulted from the redistributed charge density, the interactions between Si atoms are renormalized, leading to the phonon renormalization and the modulation of phonon anharmonicity through electron-phonon coupling. Our study paves the way for robustly tuning phonon transport in materials without altering the atomic structure, and would have significant impact on emerging applications, such as thermal management, nanoelectronics and thermoelectrics.