Abstract: Aims at a discussion on the problem of risk management in large scale scientific research projects. It puts forward a new method based on the theory of grey relevancy (GR) on the selection of technological routes and evaluation of the phase risk effects. GR can be acquired using the original data after their accumulation so as to get the relevancy matrix, from which the technological routes can be selected taking the lowest risk effect as its criterion. The risk is then sorted by priority in different phases. Furthermore, an example is given to explain the steps and the significance of this method. The method provides a tool of analysis on risk evaluation for such projects with limited number of samples and amount of information.