DOE (design of experiment) is the design of simulation cases that aims to find the variation of the performance index for the variation of design parameters. The design parameters are defined from the Design Variable Properties and Design Point Properties and the performance indexes are defined from Function Expression Properties. The objective function of the design study is defined with the performance indexes and each weight. A Parametric Study is used to find how much each design parameter influences the variation of performance indexes. Other methods of DOE are used to find which combination of design parameters is a best design for each performance index and objective function. Simulation models for DOE are automatically created and simulated. The analysis result of DOE can be used for the design sensitivity analysis, finding best or worst cases, effect analysis of tolerances, screening, and something which is related to the design study.