In order to provide an accurate mechanical environment of exterior ballistics for the safety and reliability design of fuze, a mathematical model of the motion of rotating projectile, which has dynamic unbalance angle and the axis of rotation of fuze being umparallel to the axis of projectile, around the center of mess in exterior ballistics is established based on the rigid body dynamics. The formulas of the axial, radial and tangential components of inertial force acting on fuze parts, which is caused by the motion of rotating projectile around the center of mess, are derived. The credibility of the theoretical analysis is verified by the simulation of ADAMS software. It can be known from force analysis that, when the center of axial moving parts of fuze and the centroid of bullet and axis are on the same plane, and the distance between the centroid of axial moving parts of fuze and the inertia principal axis of projectile is maximum, the axial force and radial inertia force of fuze are greatly increased compared with the traditional calculation results （the inertia force of 155 mm caliber projectile achieves several times）. The fuze axial moving parts can not be prevented from moving forward under the action of axial force even if the radial and tangential forces are far greater than axial force in the condition of periodic fluctuation and large fluctuation amplitude.