The design of 3-D inertial measurement unit（IMU） is presented

which consists of（3-D） accelerometers

3-D gyroscopes and 3-D magnetic sensors.It has characteristics with very small size

low power consumption and inexpensive

and it can be applied in the location system of micro robot and the control system of aerial robot control easily.The error sources of this IMU and the the non-orthogonal error model are analysed.The automatic initial calibration based on Newton’s method is implemented.The experiments show the calibration can reduces the offset error

scaling error and non-orthogonal error efficiently.