To solve the vehicle positioning problem caused by signal missing of satellite system, three-dimensional dead reckoning (DR) algorithm using differential odometer was given out based on gyroscope-free idea. After station equation and observation equation, improved Sage-Husa adaptive filter was adopted to raise the position precision by residual prediction. The simulation result shows that the system precision can meet the demand of positioning in short time and to be the auxiliary system of satellite position system in complex land form. The three-dimensional DR algorithm improves the system reliability for missing use of inertial navigation element.