Abstract: According to the practical experiences about old clay engineering in other regions, the foundation bearing capacity of old clay can be determined by mathematical statistics method in two ways:One is laboratory soil tests to get some data for table lookup to gain some physical and mechanical properties such as void ratio and liquid indexes; The other is insitu test to gain static sounding index and standard penetration test index. With such mature experiences and analysis on the correspondence between soil tests, in-situ test index and static load test of foundation bearing capacity, the authors summarize the empirical formula and experience table for the calculation of old clay foundation bearing capacity with soil physical and mechanical properties and in-situ test static sounding indexes.