In conceptual design, a number of design concepts and alternatives would be generated. These concepts and alternatives usually need to be evaluated to reduce the search space. However, it is not easy for the designers to determine which alternative is better, especially in the design environment where multiple designers might be involved. Current researches mainly focused on the evaluation models, but rarely provide the integrated tools to assist the evaluation process. To address this problem, we propose a web-based collaborative design evaluation platform and two evaluation principles for different evaluation situations. A design case is used to illustrate the evaluation process, where it is necessary for the designers to select a working phenomenon for the “generate force” subfunction of a nailing machine.