含义不同、用法不同、介词不同。by this way的意思是借着这种手段，表示被动；in this way的意思是用这个办法，表示主动。by this way介词为by；in this way介词为in。

by this way

By this way, we can save a lot of paper work.

这样做的话，我们可以省下很多书面手续。

Only by this way, can we hope to reduce the waste on campus.

只有通过这样的措施，我们才有希望减少校园浪费。

By this way, the drawing efficiency can be improved.

采用这种方法，可以有效提高机械图样的绘图效率。

And by this way you can

通过这种方法，你才可以。

in this way

He pulled my sleeve, attracted my attention in this way.

他扯了扯我的衣袖以引起我的注意。

In this way they can better apply theory to practice.

这样他们就能更好地把理论运用到实践中去。

In this way they brought into full play the initiative, wisdom and power of the masses.

这样他们就使群众的积极性、智慧和力量都充分发挥出来。

Only in this way can the experiment succeed.

惟有这样做，试验才能成功。