Abstract: For the issue of measuring the roll attitude of the spinning projectile with miniature inertial measurement unit (MIMU), an analysis of spinning projectile angular motion characteristics was proceeded, and a mathematical model of measuring spinning projectile roll attitude with MIMU was established, and then, a measurement method of the roll attitude of the spinning projectile was proposed based on three order phase-locked loops and MIMU. Based on the well study of three order phase-locked loops and its characteristics, the loop filter parameter of three order phase-locked loops were calculated out according to the characteristics of the spinning projectile coupled angular motion signal and the measured signal of MIMU, and the model of measuring the spinning projectile roll attitude based on three order phase-locked loops and MIMU was proposed, and the roll angular rate and roll angle could be calculated out with the proposed method. The experiments results show that, the proposed method can effectively lock the roll angular motion signal of the spinning projectile, and calculate out the roll attitude of spinning projectile with high accuracy.