建议你查一下牛津词典，注意句型和介词后用什么名词做宾语，根据例句体会用法。

We warned our children of/about the dangers of playing in the street.

Janet warned me about the water. She said it wasn't safe to drink.

这两个句子中 warned 后面所接介词为什么有区别? 是warned of和warned about在意思上有什么区别吗?

【答】warned of和warned about在意思上没有多大的区别。例如：

    以下摘自《牛津英语搭配词典》第2版：warn about 就......提出警告 No one had warned us about the unbearable heat. 没有人警告过我们注意难以忍受的高温。 warn of 关于......提出警告 They warned us of the risks involved. 他们事先提醒了我们所涉及的风险。

    以下摘自《朗文实用英语词语搭配词典》：to warn about [of] 告诫...须提防 ... They warned me about his bad temple. 他们叫我小心，说他脾气很坏。The police warned us of the pickpockets.警察告诫我们须提防扒手。

    以下摘自《张道真高级英语词典》：warn about 警告[提醒]某事: I warned you about that electric wire.  我提醒过要你当心电线。She was glad he had warned her about Jeff.她很高兴他曾警告过她有关杰夫的事。The radio warned people about delays on the roads this morning. 广播电台警告市民今晨公路上会堵车。warn of 警告[提醒]某事，让警惕：They warned her of the wickedness of her stepmother. 他们让她警惕后母的狠毒。The government is warning (the public) of possible terrorist attacks. 政府警告（公众）可能有恐怖分子的袭击。The morning paper warned (us) of serious delays at the airport. 早报提醒（我们）说机场飞机起降延误情况可能很严重。