In order to improve the measurement accuracy of micro inertial measurement unit (MIMU), an adaptive selfcalibration method of MIMU system is proposedin this paper. First, the error model of the gyroscope and accelerometer is transformed into a linear regression equation through analyzing the error model of gyroscope and accelerometer of MIMU system. Then, the MIMU system is fitted by the least square method of ellipsoid fitting. Finally, the multiple fitting modelsare used for the overall calibration. The experimental verificationis carried out on a threeaxis turntable in laboratory, and the accuracy of the calibrated attitude measurement system is improved by three orders of magnitude, confirming the feasibility of the proposed calibration scheme.