The weapon and equipment system of systems (WESoS) construction risk analysis is great significance to enhance decision-making and management level of information technology WESoS construction. The concept of "entropy" in the information engineering is using to calculate the entropy, and the entropy weight is used to fix subjective weight, after that Combining ideal point method to evaluate and select the schemes, the best decision of WESoS construction is get. The model is of impersonality and in reason, which provided a simple and practical method for construction risk evaluation of WESoS.