Through researching variation of soft clay microstructure in accelerated creep condition, we can deeply understand internal mechanism of accelerated creep characteristics. According to the micro quantitative technology and triaxial creep test of a variety of conditions of soft clay in Tianjin area, comparison between microstructures of soil samples under static and dynamic loads is made for explaining creep mechanism from microcosm. Research shows that the abundance and complexity of the structure element reduce when the accelerated creep appears, and the shape of the structural unit body becomes oblate and tends to smooth edges. Soil particle has no obvious directional property under natural condition. The particle orientation enhances obviously after the accelerated creep. Vibration loads make the creep degree increase and the soil creep rate be accelerated. It reveals that the accelerated creep of soil mass is actually a self adjusting and reengineering process of the soil internal structure under dynamic loads.