The invention discloses a method for calculating design depth of a suspended vertical separation barrier. The method comprises the following steps: determining designed service period and breakdown standard of the suspended vertical separation barrier; determining equivalent permeability coefficient and equivalent hydrodynamic dispersion coefficient of a soil layer according to characteristics ofthe soil layer between the position of pollutants and the bottom of the suspended vertical separation barrier; then directly calculating the design depth of the suspended vertical separation barrier with a corresponding calculation formula. The method has the advantages as follows: the method for calculating the design depth of the suspended vertical separation barrier is simple and fast, the design depth of the corresponding separation barrier can be calculated by determining the designed service period and the breakdown standard of the separation barrier, and a calculation result is precise.