A new approach to assisting problem solving in ill-structured management domains, i.e., a knowledge-based human and computer cooperative system, is proposed. The system includes 1) a knowledge base that stores experimental knowledge; 2) a computer inference function which uses its knowledge base logically; and 3) human association ability which uses the knowledge base intuitively. The emphasis is on cooperation of 2) and 3). In order to realize this cooperation, a guide function of human association is devised and incorporated into a computer. An example system is developed for large-scale thermal power construction project risk management. This system enables project managers to make maximum use of an experimental knowledge base so as to help them effectively control their projects. The proposed approach represents a frontier in both knowledge engineering and human-computer interaction.