The plug-in supported by vue3 should be volar. There was an old vue2 project plug-in vetur before, so an error will be reported
solution: create a new .vscode in the project and create a new file settings.json, which reads as follows:

{
    "vetur.validation.template": false,
    "vetur.validation.script": false,
    "vetur.validation.style": false,
}

Finally, restart vscode to solve the problem