In order to work in Sweden, you must have a work permit. Your application for work permit should be finalised before entering Sweden.
It is the Swedish Migration Agency that processes and decides upon your application for a work permit. For a full description of what rules apply, please visit their website.
For employment that lasts less than three months, you will also need a visa unless you’re exempted from the visa requirement for entry into Sweden. Please contact the Consulate by e-mail (generalkonsulat.shanghai-visum@gov.se) for more information about how to apply for a visa and a work permit for an intended stay that won’t exceed three months.