in order to可以用在句首或句末，但so as to只能用在句末。

如：

He got up very early in order to/so as to catch the first bus。

In order to catch the first bus,he got up very early。

（此時不能用so as to）

so as to 和in order to的漢語意思應該是一樣的“為的是，為了”。它們的英語功能也是一樣的，都可以用來引導目的狀語。它們的不同之處就在於so as to 不能用於句子的開頭，在句子開頭只能用in order to。

另外，

1。in order to 一般用in order that加從句來替換；而so as to 一般用so that加從句來替換。in order that 可以在句首，so that和so as to 一樣不能在句首。

2。

當這兩個短語後的不定式動詞的邏輯主語和句子的主語一致時，“in order to , so as to +不定式”可以簡化為“不定式”

In order to get to school on time,he got up earlier。

這個句子可以表達為下列幾種方式：In order that he could get to school on time,。。。。

He got up earlier in order to get to school on time。

He got up earlier in order that he could get to school on time。

He got up earlier so as to get to school on time。

He got up earlier so that he could get to school on time。

To get to school on time, he got up earlier。

（這種不定式有時可以表示目的以外的狀語） 。