Is it illegal for a company to imitate a patented product designer?

Illegal. Copying products that others have applied for patents is illegal and violates the Patent Law of People's Republic of China (PRC). Anyone who counterfeits a patent shall bear civil liability according to law, and the administrative department for patent affairs shall order him to make corrections and make an announcement, confiscate his illegal income and may impose a fine of less than four times his illegal income. Serious need to bear criminal responsibility.