In view of the problem of low contrast of infrared sea-skimming small target and easy interference from noise, sea clutter and cloud, which leads to tracking failure, a tracking method of infrared sea-skimming small target based on sea-sky line was proposed. Through analysis of infrared imaging system, the Pierre-Simon Laplace filter was used to suppress background noise, and according to position information of sea-sky line in image, the target area was determined and the target was detected. After detecting the suspicious target, the real target was selected by using feature information such as gray level, size and area. Experimental results show that the proposed algorithm has a good tracking effect for the infrared sea-skimming small target.