Cognitive diagnosis is a new diagnosis technology developed on the basis of modern cognitive psychology and psychometrics, modern statistical mathematics and computer science. It has been widely used in the field of English education, especially in English reading tests, because it can scientifically describe the cognitive attributes contained in the tests, accurately diagnose the language skill structure of learners, and promote personalized language teaching. It has attracted extensive attention from scholars at home and abroad. This paper reviews cognitive diagnosis from the aspects of its development, theoretical basis, application in English reading tests, difficulties and deficiencies, hoping to promote the application of cognitive diagnosis in English teaching.