Abstract: Constitution, cableless measuring principle and design of key parts of novel mine-used cableless borehole inclinometer were introduced. Working principle of the cableless borehole inclinometer is based on the synchronous technology, that is, connect the synchronous unit and probe with wire and make them synchronously work according to set time in advance; then, disconnect the wire, connect the probe to drill pipe and send it to measured point for measuring, and the synchronous unit synchronously working with the probe records the measured point; when the measurement is finished, withdraw the probe and send the measured data by the probe to the synchronous unit for calculating dip angle and azimuth angle of the measured point. The practical application showed that the cableless borehole inclinometer is reasonable in design, convenient in use, its measurement precision is ±0.2° in (+90°～-90°)dip angle and±2° in (0～360°) azimuth angle, and it meets with measurement requirement of underground borehole trajectory completely.