With the development of cognitive linguistics,a traditional view on metaphor that metaphor is a figure of speech has been challenged.A new cognitive view has taken its place:metaphor is not just a language phenomenon,but a 'cognitive instrument' in nature.Metaphor has played an important role in understanding computer English and transferring scientific concepts.This thesis aims at making a systematic study on computer metaphors through the conceptual metaphor theory by taking screen English of computer as linguistic materials,and showing that conceptual metaphors can efficiently help people to understand and remember computer lexicons and expressions.