Nowadays, theoretic and empirical research into affix acquisition in Second Language Acquisition has attracted increasing attention (Peng Tingting, 2009; Zhao Ming, 2014; Chen Jie, 2017). However, there are still few empirical studies on affix acquisition of Chinese English learners, especially from the perspective of corpus linguistics. The present research aims to find out how affixes are acquired and used in written texts by Chinese English learners. A case study was conducted based on a self-built corpus. All of the data are collected from 174 undergraduate students majoring in English at a university in central China. Compleat Lexical Tutor (v.8.3) and AntConc (v.3.5.2) are used to process and analyze the data. As is shown in the results of the research, affixes acquired and used by Chinese English learners can be divided mainly into the following categories: 1. High-frequency affixes, such as -s, -ed, -ing, etc. 2. Intermediate-frequency affixes, such as -ly, -al, etc. 3. Low-frequency affixes, such as im-, in-, ir-, etc. Therefore, the affixes that are used most frequently are -s and -es, but prefixes are seldom used in written text. The present study is beneficial for providing a crucial reference for the instruction of vocabulary and writing in colleges.