Aiming at the detection of the weak and point targets in complicated background a detection algorithm that is based on the operation of morphological filtering and frame-to-frame difference is proposed.The slow-changing characteristic of background is utilized in this arithmetic.As the arithmetic picks a method named frame-to-frame difference to eliminate the isolated singularity and give prominence to the targets，it upbuilds an efficient model to forecast background.The result shows that the arithmetic can pick out the point space targets reliably in complicated background,and it can offers convenience to further target recognition and track.