A work visa is required for foreigners who want to get salary in China. Foreigners are confused when they face tons of information online, whether China's Z visa is China work visa? If want to work legally in China, foreigner should get Z visa, residence permit or work visa?
You will see the evolution of China work visa by checking the scan of following visa pages.

2004-2005 China Z visa issued at Beijing
Z visa was work visa in China before 2007. And this visa was valid for 1 year and has multiple entrys.

2009 China Z visa issued at Hong Kong
After 2007, Z visa is issued at Hong Kong, or the country which issued the passport for China Z visa applicant. As you can see the duration of each stay became 000 days. The Entries limited to 01.
China Z visa comparison
| Before 2007 | After 2007 | |
| Visa Category | Z | Z |
| Visa Entries | Multiple | 01 |
| Validity | 1 year | 000 |
| Issue at | China cities | Hong Kong or Oversea consulate |
| Whether need convertion | No | Yes, to Residence Permit |

China Residence Permit issued at Wenzhou in 2013
Currently, the holder of China Z visa has to get residence permit (as below) in 30 days, after he/she get Chinese entry stamp.
China work visa comparison
| Before 2007 | After 2007 | |
| Visa Category | Z | Residence Permit |
| Visa Entries | Multiple | N/A (practically multiple-entry) |
| Purpose of Residence | N/A | 任职(working) |
So when we talking about getting China work visa nowadays, it contains series of steps, such as Z visa application and Residence Permit application.