The method of “coagulation+plate and frame filtration” was used to conduct dehydration experiments to solve the problem of difficulty in handling high moisture in the sediment sludge from the solid liquid separator in the mode of pond captive farming. Experiments on coagulation of sludge were conducted with types and dosage of three inorganic coagulants including polyaluminum sulfate（PAS）， poly silicate aluminum ferric（PSAF）， and poly ferric sulfate（PFS） as experimental factors， and the specific resistance of sludge and pollution properties of sludge filtrate as experimental indexes. Experiments on the dehydration of sediment sludge with plate and frame pressured filtration were conducted with the type of filter cloth， the optimal dosage of the selected coagulant， the pressure of filtration and the time of holding pressure as experimental factors， and the dehydration rate of sludge and pollution properties of filtrate as experimental indexes. The results showed that PAS， PSAF， and PFS all had significant effects on conditioning sludge. When the dosage of PSAF was 2% of the dry matter mass of sludge， the effect was optimal. At this time， the specific resistance of sludge was reduced by 97.43%， to 2.08×10¹² m/kg， with the Nemerow index of the filtrate of 3.61. Plate and frame pressured filtration had good performance of dehydration on the sludge conditioned with PSAF. The dehydration effect of sediment sludge with plate and frame pressured filtration was good， with the moisture in sludge reduced to 70.98%， the dehydration rate reaching 80.94%， and the Nemerow index in the filtrate being 4.54 when the filter cloth was made of polyester 621， the dosage of PSAF was 2% of the dry matter mass of sludge， the pressure of filtration was 0.3 MPa， and the time of holding pressure was 10 minutes. It is indicated that the approach of plate and frame pressured filtration after PSAF conditioning can be used as an effective dehydration technique for sediment sludge in the mode of pond captive farming to achieve the goal of reducing the volume of sludge to be convenient for transportation and storage.