十年前英文

ten years ago在十年前如这一切在十年前是不可能有的1. All this would have been impossible ten years ago早在十年前我就看到过他1. I saw him as early as ten years ago事情发生在十年前，当时我还是个小孩子1. It happened ten years ago, when I was a child他早在十年前就染上了抽烟的习惯1. He got into the habit of smoking ten years ago

十年前就是ten years ago，前面不需要加任何介词。

……，你这是要干嘛

one year ago, two years ago, three years ago,以此类推

in后面是一段时间

A decade ago

与一般过去时搭配的是ten years ago.与现在完成时搭配的是ten years before

ten years ago就可以了，前面不加介词