1. Add -ed directly. Such as: lack——lacked, open——opened, repeat——repeated.

2. If there is an e at the end, just add -d. Such as: live——lived, please——pleased, free——freed.

3. It ends with "a vowel + a consonant", the syllable is stressed again, double the ending consonant, and add -ed. Such as: stop---stopped, fit---fitted, chat---chatted, control---controlled.

4. For words ending with a consonant plus y, change y to i and add -ed. Such as: try---tried, study---studied.

5. The changing rules of words ending with l are equal to the changing rules of their present participles. Such as: travel---travelled＼traveled.

Extended information:

Usage

1. The past participle of a verb is used as a predicate to express state. For example: The door was broken.

2. The past participle of the verb serves as the object complement. Note: The past participle of a transitive verb serves as an object complement, has a logical passive relationship with the object, and expresses completion. For example: I'd like to see the plan carried out.

3. The past participle of the verb is used as an attributive, indicating passive or completion.