Can the property management company tear down my floor at will?

The property management company can't damage your floor casually (premise: you must be the legal owner of this floor).

According to the first chapter of People's Republic of China (PRC) Property Law:

Article 7. The acquisition and exercise of real rights shall abide by the law, respect social morality, and shall not harm the public interests and the legitimate rights and interests of others (Article 2 stipulates the civil relations arising from the ownership and use right of things, and this Law shall apply). So you can sue the property management company.