Abstract: For some complex structural problems a rigorous analysis can not be obtained due to lack of appropriate computational method. In such case the comparison method will become very important. There are a lot of uncertain factors in the problems of soil mechanics and foundation,sometimes judgement must be made by aid of regional experience. Problems of liquefaction of silty sand are especially complex. In current methods empirical formulas based on statistics are used, it is hard to find the common rules among the different formulas, thus there are some difficulties in making a reasonable design. By the comparison method suggested in this paper, the safety factors of the design may be calculated. It is -worth-while to note that by adopting comparison method for design, large economical effect can be obtained.