The research on mobile robot's autonomous navigation in the unkown environment is still a challenging advanced topic,and it requests the robot to adjust his own spatial attitude before the directional migration.The Strapdown inertial navigation has the explicit definition of the spatial attitude information which is carried out by robot's tilt angle,magnetic azimuth angle and tool face angle in detail.By considering that the spatial attitude which has been opened has flaw to resolve mathematical model,the mathematical model of the space coordinates transformation,the spatial straight line equation and the dog-leg angle's definition,in addition,the specific achievable plan is given through the triple-axis accelerometer and the triple-axis magnetometer.The experimental result indicates that this plan can get the correct spatial attitude,tilt angle within the deviation of ±0.1°,magnetic azimuth angle and the tool face angle within the deviation of ±1.5°.So it is an ideal choice for the spatial attitude measurement system on account of the low cost and the small volume.