At present, there are various methods of determining the pore size distnbution of needled nonwoven geofabrics. None of them has allowed for the features that the needled nonwoven geofabrics are thin stereo netted geotextiles with high porosity. Pores run muhidirectional and are irregular in forms. The method introduced in this paper can meet these features better. Some new resuhs obtained and analysed are reported. It provides a new laboratoiy test method for further improvement of filtration design criteria.