One type of special soil called diatomaceous was encountered during the execution of site investigation in Namibia.Its composition and microstructure was obtained by X-ray diffraction and thermal field emission scanning Its.Detailed laboratory analysis tests and various in-situ tests were carried out to gain the shear strength aiming at the special engineering properties of diatomaceous.The results show that the water content of diatomaceous is very high,the density is very low and the porosity is large.It is found that the shear strength of diatomaceous obtained by laboratory tests is consistent with that in-situ test.But compared with the shear strength,its compressibility is significantly higher appears not match with its shear strength.