Abstract:Plato proposed the justified true belief as the definition of knowledge, this definition does not include the technical knowledge, and also the Gettiered problem exists in technological knowledge. Review the historical evolution of technological knowledge classification, its evolution process has certain internal logic, and effective is the main characteristic of technological knowledge.Put forward from the Angle of epistemology with effective, belief and justified as the elements for the ternary technological knowledge definition, all kinds of technological knowledge are unified under this definition, including "technological knowledge is effective" as the centerpiece of the definition. Technological knowledge in the practice, made technical manual content to justified its effectiveness. Further discussion from the angle of epistemology for technological knowledge, it can help us parsing technology itself and echo technological knowledge ontology.