在地上一般用on the floor，尤其是表示与人有关的某件事情时。也有用in the floor的时候，但往往表达的是某个物体，更有在地里或地底的意思。用几个句子来感受一下他们的区别：
一、on the floor例句：
1.The dish smashed (up) on the floor.
碟子掉在地板上摔得粉碎。
2.He stubbed out the cigarette on the floor.
他在地板上踩熄了他的香烟。
3.They got around the lack of chairs by sitting on the floor.
他们坐在地板上克服了椅子缺乏的困难。
二、in the floor例句：
1.Yes, there are lights in the floor that are supposed to guide you. And they will if everything is working right.
的确，地面上的灯应该会指引你，如果一切正常的话。
2.We know that several depressions in the floor are deeper than Mt. Everest is high, but we cannot be sure that we have found the deepest one.
我们已经知道有几个海床坑处的深度高于珠穆朗玛峰的高度，但是我们不能确定我们已经找到了海底最深的地方。
3.The water is removed through a hose to the nearest drain, usually in the floor, that leads to machinery designed to remove radiation from the water.
这些水通过一根水管排放到最近的下水道中，通常是在地底，然后连到设计用于从水中分离放射性物质的机器上。