With the continuous advancement of oil and gas exploration and development in China, there is an urgent need to accelerate the drilling and development of deep and ultra-deep wells. In order to improve drilling efficiency and ensure drilling safety, precise control of the drill bit along a predetermined trajectory is essential. Therefore, wellbore trajectory measurement technology plays a crucial role in real-time monitoring of the wellbore trajectory drilling direction during drilling operations, ultimately ensuring the encounter with target reservoirs. However, the operating environment in deep and ultra-deep wells typically reaches temperatures as high as 175 ℃, and traditional wellbore trajectory measurement instruments have poor temperature resistance, making them unable to operate stably in high-temperature environments and difficult to accurately measure wellbore trajectory parameters. Therefore, this paper proposes a 175 ℃ high-temperature wellbore trajectory measurement system. It adopts sensors, integrated circuit chips, and discrete electronic components designed and manufactured to withstand temperatures up to 175 ℃, ensuring the system’s high-temperature resistance. The paper derives the basic principles of wellbore trajectory parameter measurement and establishes a trajectory measurement model. This model, combined with calibration algorithms, proposes error correction methods for accelerometers and fluxgate sensors based on measurement data. Laboratory testing of the system was conducted using a high-precision triaxial turntable and Helmholtz coil calibration device for wellbore trajectory parameter measurement. Experimental results demonstrate that the 175 ℃ high-temperature downhole trajectory measurement system features high measurement accuracy, good stability, and strong adaptability, meeting the needs for real-time monitoring of wellbore trajectory in high-temperature environments of deep and ultra-deep wells.