Abstract: Method of least squares was used to determine the relevance among physical and mechanical properties of soft soil in Tianjin. The results showed that there were good relevance among initial void ratio, coefficient of compressibility and water content; natural water content and void ratio,so, water content can be used to estimate certain physical and mechanical properties. The regression equation between liquid limit and plastic index was:I_P=0.43(W_L-10.8), which is different form other plasticity charts. Meanwhile, it is different from Casagrande's plasticity chart which can be described as I_P=0.73(W_L-20). Soil region should be taken into consideration during soil classification.