Soft clay contains firmly bound water, loosely bound water and free water. And adsorbed water(firmly bound water and loosely bound water) is an important influencing factor on behavior of soil creep. By using of an improved direct shear creep apparatus, exploration to the rheological characteristics affected by adsorbed water in soil is performed, and creep curve characteristics of a set of soft clay samples with different types of water is tested under the same test conditions. The test results show that the viscosity coefficient of the soft clay reduces as the increase of firmly bound water, it means that creep strain resistance decreases with the increase of firmly bound water. However, when the content of water exceeds the limit of that of firmly bound water, the creep strain resistance increases with a rise in content of loosely bound water,it is concluded that firmly bound water is a key factor affecting creep of soft soil and loosely bound water is only a secondary factor. The test results have contribution to understanding of the origins of soil rheology and are of guiding significance for improvement and perfection on existing rheology and consolidation theories of soft soil.