what are the requirments to extend f visa in Shanghai ?

hi there ,i am working in shang hai since 2007,and i have valid "z" visa .i got marriage in 2009,in Nepal with Nepalese girl,but unfortunatly we didnt register the our marriage and back to shanghai for work,for some reason i didnt go back ,so with the help of my boss she had applied the 1 month bussiness visa for china ,most probely she will be in china within few days .after that we are planning for extended visa for more 6 months .
is it possible for us to get marriage certificate in shang hai ,becouse we want to apply for depending visa .please let us know if you have some idea about this matter.
thanks