This article deals with the three key factors and the relationship between them in the teaching of translation. It is a duty for the teacher to provide practice for the students. Practice promotes better understanding, and makes it possible to seek guidance from theory. Practice cultivates the students' interest in theories, and at the same time, checks the correctness of theories. Theories stem from practice and make a generalization of practice. Comparison makes differentiation. Comparisons between English and Chinese, between the students' translation, and between the students' work and the teacher's given translation should be made. The students' merits and demerits can clearly be found out during the process. Then the teacher makes comments. The three key factors work jointly to promote the quality of the translation teaching.