Can I only go to Hong Kong with my passport?

First of all, you can only use your passport to go to Hong Kong. There are generally two kinds of passports for going to Hong Kong:

Passport has an endorsement to travel, work or stay in Hong Kong. Some China people who come back from the United States to work in Hong Kong are like this, and they don't need to apply for Hong Kong and Macao passes;

Holding a ticket to leave Hong Kong within 7 days;

I don't need to repeat the first one. Now let's talk about the problems that will be encountered in the second case:

The staff at the gateway will ask very detailed questions, such as accommodation in Hong Kong, what to do at the destination and where to live.

Will emphasize boarding, if you don't board, just stay in Hong Kong and return to the mainland, there will be corresponding penalties;

So what is the punishment?

First of all, I will be seriously questioned and have a bad attitude when I come back. In the eyes of Hong Kong people, this is illegal.

Economic punishment, about a few hundred dollars;

Restrictions on entry, as the case may be, will restrict entry into Hong Kong, which generally takes a long time.

To sum up, unless there are compelling reasons, don't stay in Hong Kong illegally after crossing the border with your passport and air ticket. In fact, if there are compelling reasons, the domestic entry-exit departments have a special green channel to help them apply for formal entry-exit documents.