Loose rock-soil aggregates(LRA) is widespread in nature environment and practical engineering. A kind of LRA that composed by strong weathered slate is selected as the research object. Firstly，the sample preparation method for LRA is achieved successfully，then based on large-size stacked ring shear apparatus，a series mechanical tests for LRA under different relative density(D_r) and different dry and wet state is conducted，the research shows that，because the restraint effect and mechanical bite among LRA is weak，the peak value in stress-strain curve is not significant，the big deformation mainly composed by interparticle friction and rolling；for the three D_r(0.30，0.35 and 0.40 respectively) conditions in experiment，when LRA keep dry state，the friction angle slightly increased from 13.18°(D_r = 0.30) to 13.97°(D_r = 0.40)，and cohesion slightly decreased from 6.95 kPa (D_r = 0.30) to 4.90 kPa (D_r = 0.40)， it means the strength of LRA nearly keeps stable in this loose range，and when the sample is wet or submerged in water also meet to this law；the peak shear stress of dry LRA is much higher than that in wet and submerged in water，the water sensitivity characteristic is obvious；D_r = 0.40 is selected as a case study, based on a comparative test，it¢s clear that in researching engineering properties of LRA，stacked ring shear test is more advantages and applicability than conventional triaxial test. This research preliminarily reveals the strength and deformation characteristics of LRA，obvious water sensitivity of LRA are very useful in quantitatively explain the mechanism for large deformation and failure of loose deposit and landslide.