Invitation letter authentication

You can ask your company to apply the invitation for you from any of these units: Municipal Foreign Affair Office, Municipal Bureau of Commerce, Foreign Economic Relations & Trade Commission, International Trade Promotion Commission or Foreign Trade and Economic Cooperation Bureau.

Thanks for your information,what about invitation letter for q1,for family visit, do I or my wife need to apply to department of public bureau also?

If the visa office requires the duly authorized invitation letter from you, you need to apply from the department. Otherwise, you don't have to do that.