not that I know of used when answering a question to mean that, judging from the information you have, the answer is no 据我所知并非如此，据我所知没有 A: Is she especially unhappy at school? 她在学校特别不高兴吗? B: Not that I know of. 据我所知没有。 A: Are you going to Washington next month? 你下个月要去华盛顿吗? B: Not that I know of. 没这回事。