With the purpose of conducting new product development or designing variant product quickly, designers need to acquire relevant design knowledge and historical experience; thus, design knowledge acquisition arose at the historic moment. In the light of basic principles, characteristics and process of adaptive genetic algorithm, some kind of design knowledge in repository need to be disposed with a series of operations such as selection, crossover and mutation etc. And with the desired requirements of that kind of mechanical products, we could get the similar design or sometimes the 'perfect' solution in the knowledge base. In this essay, we take manipulator for example to acquire design knowledge; it not only validates the effectiveness of this method but also provides a new reference of design knowledge acquisition in new product development.