Abstract: Based on the analysis for the differences between the theoretical definitions of w,w_P and w_L of soft clays and usually used their test values, in consideration of different water forms and their functions in soft clay, it is suggested that w should be redefined as the ratio of total water mass except for strong combined water and soil grain mass, where soft grain means the integrated particles of real soil grains and strong combined water. This definition can avoid the confusion between theoretical definition and test results. The limit moisture contents (w_L,w_p) and deduced plastic and liquid indexes(I_L, I_p) from limit moisture contents (w_L, w_P) are all obtained from remold soft soil test without considering the effect of the natural structure of soft soils for them. Therefore, it is proposed that introducing a structure coefficient which can get from structural study for soft soil, emends the w_L, we, I_L and I_p. Emended w_L, w_P, I_L and I_P will be conformed to natural soft soil engineering practice. Meanwhile, on the interaction between clayey particles and different form water in soft soils and different function of different form water for the soft soil deformation mechanism, implication of w_L. and w_p should be revised, that is, wp represents minimum weak combined water contents and w_L represents maximum weak combined water contents with little free water.