Polyferric sulfate（PFS）was selected as a coagulant and polyacrylamide（PAM）as a coagulant aid to pre-treat waste water from medium density fiberboard （MDF） production. This research investigated the dosage and mixing time effects of PFS and PAM. The results showed that the dosage of PFS was the most important factor. We found that when 1.8 g/L of PFS was added to the waste water and mixed for 30 seconds followed with 15 mg/L of PAM and mixed for 90 seconds,the removal rates of oxygen demand （CODcr） and suspended solids（SS）reached 64.59% and 91.06%,respectively.