Conversion refers to the transformation of parts of speech in some words while maintaining the original content unchanged in order to make the translated text sound smooth and fluent as well as more idiomatic in the target language. In E-C translation, conversion of pars of speech is one of the most important translation methods. Several different forms about conversion of parts of speech are introduced through analyzing the differences and usages between the two languages so that a better version in E-C translation can be got.