The authors presented a new measuring method of the soil thermal conductivity，the probe method， which is designed and made based on the theory of line heat source． This method is used to measure thermal conductivity of coarse sand，fine sand and silty clay in different water contents． The results that measured by the probe method are well consistent with those of QTM- D 2 ． The soil thermal conductivity increases in different levels with the increase of the water content． Compared the soil thermal conductivity measured by the probe method in laboratory with in- situ experiment，it shows that the measuring gap gradually increases with the in- crease of the depth． The reason is that the in- situ measuring thermal conductivity can reflect the actual situation of the soil mass．