Water permeability of woven geotextile, usually measured in uncompressed state or under compressive stresses, varies significantly under tensile loads. To study the permeability behaviours of woven geotextile in the tensioned state, a series of laboratory experiments were carried out on one type of woven polypropylene geotextile with tensile strength of 20-30 kN/m. The experimental results show that the permittivity of geotextile under tension load in the warp direction first decreases rapidly, then approaches to a value that is 10-25% of the one in the absence of the load. On the contrary, the permittivity increases with the increase of the tension force in the weft direction and no steady value is observed. Since the tension load in the warp direction has obviously influence on the water permeability of geotextile, about 2-3% tensile strain is recommended to be applied on the warp fibres initially for determining a reasonable permittivity in laboratory test. (C) 2013 Elsevier Ltd. All rights reserved.