at在介詞裡邊是是指在某一點（剛好就是那個點），on是指在某一點以上的地方 on the top of 在物體外部的上面at the top of 在物體內部的上面例如表示屋頂上的東西時用on房子裡的日光燈就要用at
at the top of：
1.I waited at the top of the stairs. 我在樓梯頂端等著。
2.He stopped at the top of the stairs. 他在樓梯頂端停了下來。
3.They paused at the top of the stairs, doubtful as to which way to go next 他們在樓梯頂部停住了，不知道接下來該往哪邊走。
4.Who"s at the top of your speed-dial list? 你的一鍵撥號名單上第一個是誰？
5.Someone had played a trick on her, stretched a piece of string at the top of those steps.有人搞惡作劇整她，在最高的臺階上拉了一根繩子。
on the top of:
1.You will notice that your baby has two soft areas on the top of his head. 你會注意到你的寶寶頭頂上有兩處柔軟的地方。
2.At last they saw him emerge on the top of an eminence within hail. 最後，他們看到他在一個山嶺上出現了，置身於歡呼之中。
3.She is the first woman who steps on the top of Mount qomolangma. 她是第一個登上珠穆朗瑪峰的女人。
4.Clouds are forming on the top of the hill. 雲正在山頂上形成。
5.The climbers stood on the top of the mountain, gazing at the splendid view. 登山隊員們站在山頂，凝視那壯麗的景色。
at在介詞裡邊是是指在某一點（剛好就是那個點），on是指在某一點以上的地方 on the top of 在物體外部的上面at the top of 在物體內部的上面例如表示屋頂上的東西時用on房子裡的日光燈就要用at
at the top of：
1.I waited at the top of the stairs. 我在樓梯頂端等著。
2.He stopped at the top of the stairs. 他在樓梯頂端停了下來。
3.They paused at the top of the stairs, doubtful as to which way to go next 他們在樓梯頂部停住了，不知道接下來該往哪邊走。
4.Who"s at the top of your speed-dial list? 你的一鍵撥號名單上第一個是誰？
5.Someone had played a trick on her, stretched a piece of string at the top of those steps.有人搞惡作劇整她，在最高的臺階上拉了一根繩子。
on the top of:
1.You will notice that your baby has two soft areas on the top of his head. 你會注意到你的寶寶頭頂上有兩處柔軟的地方。
2.At last they saw him emerge on the top of an eminence within hail. 最後，他們看到他在一個山嶺上出現了，置身於歡呼之中。
3.She is the first woman who steps on the top of Mount qomolangma. 她是第一個登上珠穆朗瑪峰的女人。
4.Clouds are forming on the top of the hill. 雲正在山頂上形成。
5.The climbers stood on the top of the mountain, gazing at the splendid view. 登山隊員們站在山頂，凝視那壯麗的景色。