The radius, number and distribution of soil macropores under eight types of vegetation in the semi-arid region of western Liaoning Province were investigated using water breakthrough curve and Poiseulle equation. Results showed that under the different vegetations, the radii of soil macropores ranged from 0.5 to 2.3mm; weighted mean radii varied from 0.61 to 1.85mm ; and the overall mean value was 0.95mm, nearly two times the coarse aeration porosity standard. The macropores with the radius larger than 1.4mm accounted for only 2.73% of total macropore number and between 1.5 and 1.4mm, 97.27%, which showed that large radius pores were more than small radius pores. Soil macroporosity under the different vegetations ranged from 0.95% to 5.24%, which means that soil macropores constituted a small portion of soil volume. However, the mean radius of soil macropores was significantly correlated with steady effluent rate and satu-rated hydraulic conductivity. The mean radius determined 71% variances of steady effluent rate and 50% of saturated hydraulic conductivity.