Abstract：Through analyzing the shortcoming of the traditional optimization back analysis in geotechnical engineering，the suitability of the evolutionary back analysis is proposed. Also，the weakness of the genetic back analysis is revealed. In order to overcome the defect of those optimization methods，a new algorithm——immunized evolutionary programming (IEP) based on the traditional evolutionary programming (EP) and the principles of immunized artificial system (IAS) is suggested here at first time. Combining IEP with FEM，a new back analysis algorithm——IEP back analysis is proposed. Through a simple example，the proposed algorithm is verified，and the results show that this new algorithm is very good and available for practical application.
