Terahertz radiation has broad application prospects in many fields, including high-speed communication, biomedicine, nondestructive testing, space exploration, and security. However, the development of a highly sensitive room-temperature terahertz detector is an urgent issue that must be addressed. The special optoelectronic properties of emerging topological materials open up new paths for terahertz detection. In this study, the band structure and topological surface states of the type II Dirac semimetal NiTe₂ were calculated based on first-principles calculations. NiTe₂ nanosheets were obtained by mechanical exfoliation, and metal-NiTe₂-metal field effect transistors were fabricated using integrated-circuit processing technology. The photoelectric response of the device to terahertz radiation was measured. The results show that the NiTe₂-based terahertz detector has a high response rate of 2.44 A/W and a noise equivalent power of approximately 14.96 pW/Hz^1/2. Particularly, even at a zero bias voltage, the response rate remains 2.25 A/W, and the noise equivalent power decreases to 9.55 pW/Hz^1/2. These characteristics are better than those of similar terahertz detectors, and the device is stable in air and has excellent linearity within a certain range. These results are of great significance for further promoting the practical application and integration of room-temperature terahertz detectors.