In order to detect the subpixel-

point- and a few pixel targets from low SNR image sequence

this paper presents a new approach which can greatly suppress UCN-sequence through adaptive threshold detection in single frame and high order cross-correlation with multiple frames.The number of candidate target trajectories and the quantity of data processing are greatly compressed by using the approach

and the approach is compatible with infrared- and television image sequences.The theoretical analyses of various kinds of operations are expounded in the paper.The experimental results have proved the correctness of theoretical analyses and the feasibility of the optimal algorithms.For the image sequences with SNR 1.5~0.5

after adaptive threshold detection in single frame and twice high order cross-correlation

the nonzero points left are only 0.03~14.59%

and the noise rejection rate is 99.97~85.41%.