Nominalization is a very prominent phenomenon in English written language as well as in other languages. It is in close relationship with registers that it has become one of the properties for formal style writing like technical writing or legal writing. However, this does not necessarily mean we should use as many nominalizations as possible in formal registers. Overuse of it is sure to cause problems.This paper studies nominalization under the framework of Functional Grammar, which regards nominalization as a device for Ideational Metaphor that belongs to Grammatical Metaphor. In order to see how to use nominalizations correctly and what is the difference between its use by foreign language learners and native speakers, two subjects were chosen to carry out a quantitative study: Chinese MA candidates majoring in English linguistics who represent advanced foreign language learners, and English-speaking linguists who represent highly literate English native speakers.It is concluded that the use of nominalization by native speakers constitutes a higher proportion but not absolutely, owing to varied topic and different styles in writing by different authors, as well as the phenomenon of ’distillation’. The awareness of using nominalizations in written discourse, especially in scientific discourse, should be raised.