My husband is a Canadian citizen. Can I work in the office?

Yes, there is no nationality restriction for spouses of national civil servants. You can apply.

If you don't intend to immigrate after marriage, you can keep your China nationality. If you need to apply for a Canadian visa after marriage, you can apply for family reunion or temporary resident visit. It depends on the specific situation at that time. If you settle down, it shouldn't be difficult to keep your China citizenship, but if you want to be naturalized in Canada, you should know that China doesn't recognize dual citizenship, and once you become a Canadian citizen, you will automatically give up your China citizenship.