This paper developed a measurement-while-drilling instrument based on predigested inertial measurement unit (PIMU) and presented a PIMU design with a rotational modulation device, thus improving precision of inertial sensors. Then, this paper proposed an integral surveying method based on inertial navigation system and dead reckoning, measuring motion parameters characterized by long-term high accuracy. The semi-physical simulation was conducted under the laboratory conditions. The results indicate that, the suggested methodology dramatically improves measuring accuracy of attitude angles (azimuth, pitch, and roll) and position.