Terahertz (THz, 0.3–10 THz) radar systems have garnered significant attention due to their superior capabilities in high-precision and robust sensing. However, the susceptibility to jamming, along with the sensing precision loss and ranging ambiguity induced by inflexible implementation of the conventional radar signal source, presents major challenges to the practical deployment of THz radars. Herein, a flexible photonic chaotic radar system is proposed at the THz band and investigate the ranging performance in precision and ambiguity. The photonic heterodyne detection scheme facilitates the generation of optoelectronic feedback loop-based THz chaos at 300 GHz, achieving a seamless connection between THz domains and optical domains. The system is experimentally demonstrated its superior performance of sub-centimeter resolution with 0.9345 cm and ranging unambiguity simultaneously. This work bridges the THz gap in the practical deployment of chaos theory and will pave the way for a new regime of THz radar empowered by chaos.