The relationship between the secondary consolidation coefficient and pressure for soft soil is studied by indoor compression test. It is found that the secondary consolidation coefficient-pressure curve of over-consolidated soil and normal consolidated soil can be fitted by a power function and a hyperbola function, respectively. Based on the experiment, the conventional secondary consolidation formula was corrected and a modified one was proposed considering the effect of pressure and the convergence characteristic of calculation. The results of its application to an engineering project show that the new formula can better reflect the secondary consolidation characteristic of soft soil, indicating great engineering value.