This research employed the freeze-thaw treatment method under nature and manual condition to reduce the moisture content of the contaminated sewage river sediment, thus reduce the secondary pollution to environment during remediation of sewage river. Experimental results show that the freeze-thaw treatment influences the sediment dewaterability and characteristics, such as specific resistance to filtration, moisture content, granule distribution, pollutant content of leachate. After freeze-thaw treatment, the surface area of the sediment became decreased, average granule diameter increased and the solid and water separated clearly. Moisture content was decreased from 83% - 85% to 50% - 60%. Volume cavernous water, capillary water and adhesion water dissociated from the sediment, thus sediment dewaterability is enhanced greatly. The specific resistance was reduced from (1.2 - 4.1) x 10(9)s(2)/g to (3.8 - 5.2) x 10(7)s(2)/g. On the other hand, leachate characteristics changed a lot: suspend solid (SS) content was reduced from 1 000 - 1 200 mg/kg to 340 - 380 mg/kg, ammonia nitrogen content was reduced from 150 - 170 mg/kg to 100 - 120 mg/kg, BOD5 content was reduced from 300 - 310 mg/kg to 50 - 60 mg/kg, however oil content was increased from 1 - 2 mg/kg to 11 - 12 mg/kg. Therefore, if the sediment is not contaminated by oil, the leachate pollution can be reduced by freeze-thaw treatment method.