If you marry before your application is approved, you must add her in your application. That will prolong the total processing time, likely around half a year or a year. Or you can marry after you get your GC, then apply for her GC on family-base, during which she has to stay in China while you have to stay in Canada and have a job, that will take about several months, mostly less than 1 year to get her GC. Either way depends on when you want to get married and no huge difference regarding processing time.
If you get married and don't add her in your application before your case is approved, you might face trouble in future. Also, there will be less chance for her to get visit visa after marriage.