by foot是一种动词，on foot表示名词。一般情况下，我准备步行去哪里，用by foot，一般现在时用on foot。

by foot例句

It'd take weeks to get there by foot.

徒步走到那里要好几个星期。

Also the software provides a tool to analyze inversion results foot by foot.

STRATA还提供了分析分步反演结果的工具。

The main method of transportation in the Expo site is by foot.

世博园区内最主要的交通方式是步行。

Approaching Technology about Beat Ball by Foot in Volleyball Match

排球比赛中脚击球技术初探。

on foot例句

he city is best explored on foot.

最好是徒步考察这个城市。

We came on foot.

我们是走来的。

I left my car in a lay-by and set off on foot.

我把车留在路侧停车带，徒步而行。

He got up at four and set out on foot to hunt black grouse.

他4点钟起了床，徒步出发去猎杀黑琴鸡。