Is it possible to find lockers in China transport stations? I'm interested in Beijing Xi, Xian, Zhengzhou, Zhangjiajie, Guiyang, Guilin train stations. What about bus stations? What about Beijing international airport?
Most major airports in China have lockers that you can use. I can personally say that I know there are lockers at the Beijing (PEK) and Shanghai (PVG) airports. Often these are used by people who are on a transit-visa, especially the newly implemented 72-hour free transit-visa available in some of the major Chinese metropolitan cities (including Beijing).
Otherwise, this is really something you need to ask for about specific locations. Services at transport hubs will vary, regardless of where in the world you are.