I am a South African citizen visiting China for few days and lost my passport.

First, you need to go the local police station of the place where you lost the passport to report your loss and get a loss certificate. Then go to the exit and entry administration to report the loss. Next, take the loss certificate to SA embassy and apply for a new passport or travel document. Last, return to the exit and entry administration to apply for an exit permit.

As for the specific procedures and duration to get a new passport, please contact the embassy to inquire about it.