take sb.aback 表示“使某人吃惊”或“使某人吓了一跳”.be taken aback 是take sb.aback的被动式,意思是“（某人）处于惊愕状态”或“（某人）被吓了一跳”.
take sb.back 表示“使某人回想起过去”；take sth.back 表示“收回所说的话或所写的东西”,即“把…收回/取消”.be taken back 是take sb./sth.back 的被动式,意思是“某事被收回/取消”或者“某人被带回到过去”.
前者指人,后者指既人也指物.因此,be taken aback 要用人作主语.be taken back 可以用人作主语或也可以用物作主语.例如：
I was momentarily taken aback.我一时被吓呆了.
The little girl screamed and we were taken aback.小女孩的尖叫声吓了我们一跳.
I am taken back by the story.这个故事使我想起了过去.
If I buy something and he doesn't like it,I'll have it taken back.要是我买的东西他不喜欢的话,我就会把它退掉.