With the rapid development of the global military， missiles play an increasingly important role in modern war. The realization of precise guidance for missiles has become an important problem to be solved at present， and the optical seeker is an important equipment to realize precise guidance. The traditional gimbal optical seeker has many disadvantages such as large volume， high cost， and complex structure， so the strapdown optical seeker appears. Although the strapdown optical seeker can effectively solve the problems above， its detector is fixed on the missile. In addition， there are problems such as high noise， attitude coupling， and phase matching， and the strapdown optical seeker requires high filtering/estimation algorithms. In this paper， the principle， composition， and application background of strapdown optical seekers are introduced， combed， and summarized. Through the simulation of the estimation effect of adaptive unscented Kalman filter and unscented Kalman filter， it is found that the adaptive unscented Kalman filter has higher accuracy. Finally， the future development in this field is prospected.