It depends on many factors. If your wife is coming on your Z visa as your spouse then she will not be entitled to work on that visa. She would have to get her own work visa. In order to obtain a work visa she would need a job offer and an invitation letter from a company in order to apply for a work visa. Also to be eligible to get a work visa she would have to meet strict criteria i.e have a BA degree etc. So essentially if she is qualified in an area that there are jobs in China then she should be able to secure work. But if she has no formal qualification she will not be able to work in China.
Areas that foreigners can work in in China fall under the category of ‘foreign expert’. Essentially “foreign expert’ jobs are those that are deemed important for China’s economic & social development. Those who are eligible for ‘foreign expert status’ e.g. teachers, scientific researchers, senior management professionals etc are invited by the Chinese government or a multinational or other organization to work in the country. Without such an invitation, one cannot get a work visa.