He travels on business.

He is aways on business.

句1，on business 是介词短语，作“目的状语或伴随状语”。这里，travel 不是“旅游”，而是一个位移动词“前去”，等于 go。go on business。译为：“他出差去了。”

句2，on business 是介词短语，作“表语”，指人处在某种状态中。译为：“他总是出差”。

on 跟某些动词连用，引出所进行的活动，特别在旅行方面。意为“处于...情况中，从事…中”（We use on to introduce an activity that someone is doing, particularly travelling. ）。这说明，介词 on 跟 go 连用，表示“从事于某种活动”。例如：

go on business

I will go on business either this week or next week. 我将在这星期或下星期出差。

go on a holiday

I'd love to go on a holiday but I can't afford the time. 我倒想去度假,可是抽不出时间来。

go on a trip

As the day was fine, they decided to go on a trip. 由于天气好,他们决定作一次短途旅行。

go on a tour

We are going on a tour of the city this afternoon. 我们今天下午要到城里去观光。

go on a vacation

He never goes on a vacation but he takes his pet dog. 他每次度假都会带他的狗去。

go on a diet

The doctor says I've got to go on a diet. 医生说我得节食。

go on strike

The workers go on strike to ask for higher pay.为了提高工资，工人们举行了罢工。

go on a hike

We took advantage of the fine weather to go on a hike. 我们利用晴朗的天气去旅游。

go on a journey

He made a resolve to go on a journey early in the next morning.他决意明天一早就动身。

go on a voyage

Captain Cook went on a voyage round the world.库克船长做了一次环球航旅行。

go on an excursion

Weather permitting, we'll go on an excursion to the Western Hills tomorrow.天气要是合适,我们明天将去西山去玩。

go on an expedition

The scientists will go on an expedition to the South Pole.这些科学家们将要去南极考察。

go on an outing

I'll go on an outing with some friends.我与朋友去郊游。

go on an errand

My mother asked me to go on an errand; she wanted me to buy some food.我妈妈叫我跑一下腿，她想让我去买点食物。

go on a picnic

We will play sports or go on a picnic. 我们将做户外运动或去野餐。

go on business

I will go on business either this week or next week. 我将在这星期或下星期出差。