Abstract: Algorithms for the updating of terminal guided projectile attitudes update are studied. Mathematical models are established. Traditionally, the quaternion method is adopted to calculate the attitude angles and its precision is satisfied. But the rotation vector method was tried and a simulation about it was done using the terminal guided projectile' trajectory data. Its precision was compared to the quaternion's. And the results showed that the rotation vector method works well and because it overcomes the unchangeable error happens when rigid body rotate, it has a higher precision whether when the attitudes updating periods are the same or when the sampling periods are the same.