In order to explore the influence rule of fine particle content on the permeability of ocean ultra-fine sands and the meso-mechanism, the particle gradation of the ultra-fine sands from the coast of Mauritania was analyzed by a sieving method combined with laser particle size analyzer. According to the results of the particle gradation, the ultra-fine sands with different fine particle contents were configured indoor for variable head penetration test. Finally, combined with the SEM technology, the influence mechanism of permeability coefficient of fine particle content on ultra-fine sands was preliminarily explored. The results show that the content of fine particles changes the pore distribution structure of ultra-fine sands and the integrity of the sample in the microscopic view, thereby affecting the permeability coefficient. The content of silt fine sands (d=0.075~0.1mm) has minor effect on the saturated permeability coefficient k20of ultra-fine sands, and is linearly related. The content increases by 5%, k20 decreases by about 0.2×10-3cm/s. The content of fine particles (d ≤0.075 mm) has a relatively large influence on k20, showing a power function that first decreases and then stabilizes. The relationship between k20 and the fine sand gradation state parameters Cu and Cc is more accurately expressed by a power function.