Forest is an important type of ecosystem on land. Although the area of karst forest is relatively small, its soil water holding function is still important for soil and water conservation and ecological restoration in karst area. Taking the typical karst forest land in Guizhou as an example, the physical characteristics and water holding characteristics of soil under different forest types were analyzed by field sampling and laboratory experiment. The results show that the soil bulk density increases with the increase of the soil depth，while the soil porosity decreases with the increase of the soil depth. In the case of limestone soil, the order of the mean value of soil bulk density of different forest types from large to small is coniferous forest>broad-leaved forest> mixed forest, and the order of the effective water holding capacity of different forest types from large to small is broad-leaved forest> mixed forest> coniferous forest. The soil bulk density in coniferous forest growing on yellow soil was lower than that in coniferous forest growing on limestone soil, and the difference of soil porosity in the two forest types was not obvious. Most of the water holding capacity index in coniferous forest growing on yellow soil are slightly larger than that in coniferous forest growing on limestone soil coniferous forest, except the capillary water holding capacity. The maximum water holding capacity of karst forest depends largely on the soil bulk density, and the impact of capillary porosity on the maximum water holding capacity is not significant.