Abstract: Both mechanical analysis and simulating experiment of boudinage indicates its non-Newtonian fluid behaviour.This paper attempts a quantitative evaluation of the rheolegical parameters of rocks from a study of the boudinage structures in Xishan,Beijing.The authors obtain a stress exponent between 3.06 to 7.69,for the calcite-quartzvein embedded in cipolino and a viscosity ratio for the two varying from 8.74 to 20.27;a stress exponent of 2 57 to 4.75 for the quartz vein in slate and a viscosity ratio of them ranging from 94.8 to 175 8;and a stress exponent between 2.25 and 3.93,for the siliceous bands interbedded in dolomite and a viscosity ratio between them varying from 2.38 to 4.26.