| Acknowledgements | 第5-6页 |
| Abstract in Chinese | 第6-8页 |
| Abstract in English | 第8-10页 |
| List of Abbreviations | 第13-17页 |
| Chapter One Introduction | 第17-22页 |
| 1.1 Background of the Research | 第17-19页 |
| 1.2 Significance of the Research | 第19-20页 |
| 1.3 Organization of the Research | 第20-22页 |
| Chapter Two Literature Review | 第22-39页 |
| 2.1 Lexical Richness | 第22-28页 |
| 2.1.1 Definition and Classification of Lexical Richness | 第22-24页 |
| 2.1.2 Aspects and Measures of Lexical Richness | 第24-28页 |
| 2.2 The Importance of Lexical Richness | 第28-29页 |
| 2.3 Previous Studies on Lexical Richness | 第29-36页 |
| 2.3.1 Study of Lexical Richness Abroad | 第29-33页 |
| 2.3.2 Study of Lexical Richness at Home | 第33-36页 |
| 2.4 Lexical Features of Chinese Learners' Writing | 第36-39页 |
| Chapter Three Research Methodology | 第39-50页 |
| 3.1 Research Questions | 第39页 |
| 3.2 Corpus-based Approach | 第39-42页 |
| 3.3 Research Instruments | 第42-46页 |
| 3.3.1 Corpora | 第42-43页 |
| 3.3.2 Software | 第43-46页 |
| 3.4 Research Design | 第46-47页 |
| 3.5 Data Collection | 第47-48页 |
| 3.6 Research Procedures | 第48-50页 |
| Chapter Four Results and Discussions | 第50-71页 |
| 4.1 Comparison of Lexical Variation | 第50-53页 |
| 4.1.1 Comparison Between High Grade Students and Low Grade Students | 第50-51页 |
| 4.1.2 Comparison Between Chinese English Major Students and ChineseNon-English Major Students | 第51-52页 |
| 4.1.3 Comparison Between Chinese English Major Students and Native Speakers | 第52页 |
| 4.1.4 Summary of Lexical Variation Comparisons | 第52-53页 |
| 4.2 Comparison of Lexical Sophistication | 第53-58页 |
| 4.2.1 Comparison Between High Grade Students and Low Grade Students | 第54-55页 |
| 4.2.2 Comparison Between Chinese English Major Students and ChineseNon-English Major Students | 第55-56页 |
| 4.2.3 Comparison Between Chinese English Major Students and Native Speakers | 第56-57页 |
| 4.2.4 Summary of Lexical Sophistication Comparisons | 第57-58页 |
| 4.3 Comparison of Lexical Density | 第58-62页 |
| 4.3.1 Comparison Between High Grade Students and Low Grade Students | 第59页 |
| 4.3.2 Comparison Between Chinese English Major Students and ChineseNon-English Major Students | 第59-60页 |
| 4.3.3 Comparison Between Chinese English Major Students and Native Speakers | 第60-61页 |
| 4.3.4 Summary of Lexical Density Comparisons | 第61-62页 |
| 4.4 Comparison of Lexical Error | 第62-67页 |
| 4.4.1 Comparison Between High Grade Students and Low Grade Students | 第63-64页 |
| 4.4.2 Comparison Between Chinese English Major Students and ChineseNon-English Major Students | 第64-65页 |
| 4.4.3 Comparison Between Chinese English Major Students and Native Speakers | 第65-66页 |
| 4.4.4 Summary of Lexical Error Comparisons | 第66-67页 |
| 4.5 Summary of Lexical Richness Research | 第67-71页 |
| 4.5.1 Features of Lexical Richness Comparisons | 第67-69页 |
| 4.5.2 The Advantages and Limitations of Chinese English Major Students | 第69-71页 |
| Chapter Five Conclusion | 第71-77页 |
| 5.1 Major Findings | 第71-74页 |
| 5.2 Implications | 第74-76页 |
| 5.3 Limitations | 第76-77页 |
| Bibliography | 第77-83页 |
| Papers Published During the Study for M. A. Degree | 第83页 |
