After existing study methods are analyzed, a new researching model for conceptual design based on extension and genetic algorithms was presented. The inner-model and outer-model of product project were set up with matter elements. In genetic algorithms the coding for individual, the means for cross-over and mutation were all founded based on the inner-model. The fitness function was set up combined with relationship function. The technique solves the innovative and incompatible problems in conceptual design. The feasibility of the new researching model is testified by three conceptual design examples for retarder.