Researchers usually focused on using unstructured documents, such as news, scientific literatures, World Wide Web pages, business reports, as input documents of KeyGraph. But the unstructured documents might results in unclear keywords and meaningless keywords. Although traditional document preprocessing could dismiss some of the problems, generating complex and unreadable KeyGraph diagrams were not avoidance. In this research, we applied the concept of chance discovery and KeyGraph to discover hidden blue ocean strategy (BOS) for decision makers who not necessary familiar with the concerned domains. A preprocessing strategy, including develop an operational framework of BOS and design a sentence structure for representing BOS, was proposed to assure the necessary keywords be included in the required documents. Seventy-two documents concerning blue ocean firms were collected as sample cases for developing the operational framework. At last, three experiences were designed for confirming the performance of the proposed preprocessing strategy. Experimental results shown that the subjects were not consistently recognized BOS with traditional approach (used unstructured documents as input documents of KeyGraph). In contrast, the subjects could easily find explicit scenarios of BOS, and recognize a few of implicit scenarios appeared on KeyGraph diagrams with the proposed strategy.