Green Card of China means Permanent Residence Permit, if you have it, you can travel China freely without a Chinese visa. But it is very hard to get a Chinese Permanent Residence Permit, you can see the regulations on this website https://www.travelchinaguide.com/embassy/visa/refusal.htm

If you are only seeking to work in China, you can obtain an offer of employment from an employer certified to employ foreigners. If you can meet the required conditions you will granted a Z visa which can then become a temporary residence permit for the duration of your contract. See: www.travelchinaguide.com/embassy/visa/work.htm