Abstract: A free gyro is generally used as the reference for missile attitude control in the control system of antitank missiles, and the gyro-rotor in such cases is often spun in inertial rundown. It has been verified from theoretical analysis and experiments that precision of a gyro is reduced as a result of gyro -rotor inertial rundown. In order to satisfy the precision needed in a control system, mounting of gyroscopes in the missile must be carried out in accordance with specific criteria. The highest speed of gyro -rotor must be restricted when gyroscopes are designed, in order to improve the precision of gyroscopes. On the condition that the average moment of momentum of gyroscopes is kept unchanged, reducing the speed of gyro-rotor appropriately and raising the moment-of-inertial of the rotor prove to be feasible ways in enhancing the precision of gyroscopes.