In the event that you no longer want to use the passcode on your Apple Watch, it’s easy to disable it. On the smartwatch, go to Settings app → Passcode → Disable Passcode.
You can also turn off the passcode from your iPhone. Go to the Apple Watch app on the smartphone → Tap on My Watch → Tap on Passcode → Tap on Turn off Passcode.
Before you take either of these steps, make sure you really want to disable the password. You’ll need it enabled on your Apple Watch to use features such as Apple Pay.