Abstract: When borehole trajectory parameters are measured while drilling by a measurement system of triaxial accelerometers, fluxgates, and rate gyros, the results show huge deviations due to the influence of factors such as rotation, vibration, and magnetic interference, etc. As a result, the requirements of geosteering while drilling cannot be met. Considering this, a quaternion-based measurement model of borehole trajectory parameters was built for the above measurement system. In addition, according to state equations and measurement equations, three strap-down Kalman filters and a correction system for magnetic interference were applied to filter and correct accelerometer and fluxgate signals. In this way, a dynamic measurement method of near-bit borehole trajectory parameters based on data fusion was developed. The simulations in the laboratory and on-site drilling showed that the measurement precision of borehole trajectory parameters was significantly improved by using the proposed method. The research indicates that the proposed method can eliminate the influence of rotation, vibration, and magnetic interference on the results of the measurement system of triaxial accelerometers, fluxgates, and rate gyros while drilling to upgrade the measurement precision for geosteering, thus meeting the requirements of geosteering while drilling.