16 January 2017 Last updated at 12:32 GMT
The ceremony is called the inauguration.
At the event, he will make a promise to do the best for the country and will give a speech known as the inaugural address.
There are a few traditions passed down, which he must observe on his inauguration day.
Leah takes a look at what's going to happen throughout the day...
On Friday, Donald Trump will officially become the next president of the United States.