To understand creep mechanism of soft clay, one-dimensional consolidation creep tests, bound water measurement tests, and scanning electron microscope (SEM) tests on Shanghai mucky clay are conducted. The variations of bound water and microstructure in the process of consolidation-creep are quantitatively analyzed. The results show that, free water discharged under condition of p?k. Meanwhile, the creep strain and steady-state creep strain rate increase significantly. The creep process is dominated by osmotic bound water. The microstructure is solidified gradually with bound water discharging and the water content decreases exponentially with increasing loads. Deformation of soft clay is caused by consolidation-creep coupling effects. The original loose skeleton-flocculated structure translates into dense reunion-flocculated structure. The directionality of particles decreases under the long-term creep adjustment. The quantity of fine pores increases massively after creep tests and the pores with diameters less than 1 μm in dominancy. The response mechanism among loads, bound water and particles can explain engineering phenomenon well.