no wonder在句子中一般为副词，加强说话人的语气；而It is no wonder是一个完整的句子，一般用在主语从句中，一般惯用的句式为It is no wonder that……no wonder和It is no wonder都是“难怪”的意思。

no wonder例句

No wonder my brother wasn't feeling well

难怪我兄弟感觉不舒服了。

It's no wonder the piano kept going out of tune.

难怪钢琴一直不在调上。

No wonder he could hardly contain his indignation.

难怪他几乎抑制不住自己的愤怒。

It is no wonder例句

It is no wonder that you did not go.

怪不得你没走。

It is no wonder that the children love to visit the farm.

孩子们喜欢去农场玩是不足为怪的。

It is no wonder that she failed her final examination.

她没能通过期末考试，那是不足为怪的。