spacebar works like power button

If it's sleeping that's normal. Just one way to awaken the Mac. Are you sure you actually shut down?

galaxyzzz wrote:

my device is macbook 13" M1, 2020. Macos version 12.0.1

The current stable release of Monterey including bug fixes, is macOS 12.4 —I would start there and compare your results.

Keep your Mac up to date - Apple Support

Keep your Mac up to date - Apple Support

galaxyzzz wrote:

I don't know why my spacebar could work like the power button.

When my mac was off, clicking on spacebar would turn on my mac. ( it's not normal right? )

I know it's not a big problem, but could anyone explain it and how to fix it to get back to normal?

Well you do not say what exact Mac or what exact macOS—

but I can say this is the "new" way... or the 'new normal'

you can read more

Log out, sleep, wake, restart or shut down your Mac:

Put your Mac to sleep or wake it - Apple Support

Shut down or restart your Mac - Apple Support