On the basis of wide investigations and practical experiences for many years, the free expansive rate, δ_ef, being more than or equal to 40% and used as an universal index of initial judgement is considered not suitable enough for various expansive soil areas, and the indexes for intensively determinating including their applicable scope are put forward. The values of ground deformtion due to swelling and shrinkage calculated according to the Technical Specification for Buildings in Expansive Soil Area( GBJ 112-87 )are found to be of difference from the measurements, and a suggestion for solving the problem is given herein. The functions of the cushion and the sand pocket foundation are also analysed.