英语短语"can't help"（完整形式为"cannot help"）是高频表达，核心含义是"忍不住；禁不住；无法抑制"，强调因情感或外界刺激而自然产生的行为，难以控制。
表示主观上无法克制某种情绪或行为，常对应中文的"忍不住/禁不住（做某事）"。
后面接动名词（doing），表示"忍不住做某事"。
例：When I saw the puppy's cute face, I couldn't help smiling.（看到小狗的萌脸，我忍不住笑了。）
She can't help crying every time she watches that sad movie.（每次看那部悲剧电影，她都忍不住哭。）
He can't help eating snacks when he's working late.（熬夜工作时，他忍不住吃零食。）
后面接动词原形，含义与"can't help doing"几乎一致，可理解为"不得不/忍不住做某事"（更强调"无法避免"）。
例：I can't help but feel proud of my sister's achievement.（我忍不住为姐姐的成就感到骄傲。）
When he tells jokes, you can't help but laugh.（他讲笑话时，你忍不住会笑。）
注意："help"本身有"帮助"的意思，因此"can't help (sb.) with sth."表示"无法帮助（某人）做某事"，不涉及"忍不住"，需与上述用法区分。
例：I'm sorry, I can't help you with your homework—my math is terrible.（抱歉，我帮不了你做作业——我数学太差了。）
She can't help with the party preparations this weekend—she's got a meeting.（这周末她帮不了筹备派对——她要开会。）
不要混淆"can't help doing"（忍不住做）和"can't help to do"（不能帮忙做）：
❌ 错误：I can't help to laugh.（应为I can't help laughing.）
✅ 正确：I can't help laughing.（我忍不住笑。）
✅ 正确：I can't help to carry the box.（我帮不了搬箱子。）
| 结构 | 含义 | 例 |
|---|---|---|
| can't help doing sth. | 忍不住做某事 | I can't help crying. |
| can't help but do sth. | 忍不住/不得不做某事 | I can't help but agree. |
| can't help (sb.) with sth. | 无法帮助（某人）做某事 | I can't help you with this. |