Concerned with the fact that negative backwash effects commonly exist with foreign language tests in China, which exerts undesirable results in the teaching of foreign languages and the intellectual development of young people, the paper analyzes its origin in the processes of test preparation and test using, the former providing the basis while the latter being the condition under which the former takes effect. Negative backwash effects influence the teachers’ choice of textbooks, teaching contents, teaching methods and their attitudes towards students. Meanwhile, they also influence the students’ learning objectives, learning contents, classroom performance and choice of extracurricular reading materials. The article reveals that the nature of negative backwash is the surrender of test validity to implementation simplicity, of teaching construct to competition pressure, of language ability to test patterns, of study skills to test-taking skills, of critical thinking to standard answers and of the pleasure of discovery to the stress of examination. The article then puts forward suggestions on related policies and the design of tests.