Abstract: Analyzed and compared both MRP and quaternion algorithms' characteristics by (simulations).The satellite is equipped with CCD(Charge Coupled Devices) as the sole attitude (sensor) on board,and was disturbed by the first-order Markov force moment.Both MRP and (quaternion) algorithms were used to represent attitude,and UKF(Unscented Kalman Filter) was used to estimate the satellite's attitude and azimuth angles and angular rates.The computational burden of MRP is only half of currently used quaternion,while has better and less memory(consumption),because the quaternion standardization leads to singularity problem,but the MRP singularity problem is addressed by MRP switching.