How to determine projection of the following map. It is a scan of an image.
As it is China and it's a wide country, you may have to try some EPSG codes for this area. It does look like a Lambert type projection, as it goes around the north pole...
Go to EPSG website : http://www.epsg-registry.org and put in China in the Area box. Or you can try this new version : https://epsg.io/?q=China. You will get a list of existing projections on this area.
You can also browse the Georepository : http://georepository.com
It's quite difficult to tell with no other indication. My advice would be to try to regenerate this map with some China administrative boundaries and compare the output.
EDIT : I had a try with some projection, for the fun, and try to recreate your map :)
The one that fits nicely and is close to your map is a Lambert-type one as I guessed : EPSG:3415 / WGS 72BE / South China Sea Lambert