核心规则
doing 作动名词时把动作作为活动或概念，可作主语、宾语、表语和定语；作现在分词时常修饰名词、补充宾语或充当状语，通常与逻辑主语构成主动关系。
结构与例句
| 功能 | 例句 |
|---|---|
| 动名词作主语 | Learning a language takes patience. |
| 动名词作宾语 | She enjoys solving puzzles. |
| 分词作定语 | the students waiting outside |
| 分词作宾补 | I saw them crossing the street. |
| 分词作状语 | Hearing the news, she smiled. |
使用场景
介词后通常使用动名词：by practicing、without checking。某些动词只接 doing，某些接 to do，另一些两者皆可但意义不同，应结合动词搭配学习。
常见错误
错误： He is interested in to learn English. → 正确： interested in learning。
错误： Reading the report, several errors were found. → reading 的逻辑主语不能是 errors，应明确执行者。
易混知识点
used to do 表示过去常常；be used to doing 表示习惯于；be used to do 表示被用于做。三个结构中的 to 性质不同。
总结
先判断 doing 是把动作当名词还是用来修饰，再核对逻辑主语、动词搭配和时间关系。
高中必修 · 动名词与现在分词的基本功能
基本功能
动名词短语作主语通常按单数处理：Reading aloud helps pronunciation。需要明确逻辑主语时，可使用形容词性物主代词或名词所有格，正式表达如 his arriving late。
现在分词作状语可表示时间、原因、结果、条件或伴随，其逻辑主语通常就是主句主语：Knowing the risks, we prepared carefully。自然结果可用 doing 表示：The storm damaged the bridge, causing delays。
小练习
- 填空：___ (exercise) regularly improves sleep.
- 填空：___ (not know) the answer, he remained silent.
- 改错：Walking through the park, the rain began.
参考答案
Exercising。Not knowing。- 应让主句主语与 walking 的执行者一致，如
Walking through the park, we felt the rain begin。
选择性必修 · doing 的完成式与被动式
进阶形式
having done 表示主动动作明显早于谓语：Having checked the data, she wrote the report。being done 表示正在承受动作；having been done 表示被动动作已经完成：Having been warned of the storm, the hikers changed their route。
并非所有先发生动作都必须用完成式；若先后关系由连词或常识已清楚，普通 doing 也可能自然。完成式用于需要特别强调时间先后的场景。
小练习
- 填空：___ (finish) the survey, the team began to analyze the results.
- 填空：The issue ___ (discuss) now has attracted attention.
- 填空：___ (give) enough time, the experiment produced reliable results.
参考答案
Having finished。being discussed。Having been given。