The invention provides a sludge treatment method. The method comprises the following steps: step one, adding polychloride aluminum in the sludge, stirring and mixing to change the granularity size of the sludge; and step two, dehydrating the sludge obtained in the S1, wherein the dehydrating comprises repeatedly feeding materials and repeatedly mechanically dehydrating so as to obtain the dehydrated sludge. The method provided by the invention has the effect that the sludge with water content of 80% can be dehydrated to about 50% through the mode of adding less medicaments and using a high-pressure plate frame, the process is simple, and the dehydrating effect is good. Furthermore, the dosage of a conditioner is greatly reduced, especially the lime is unnecessary, the heat value of the sludge cannot be influenced, and the dehydrated sludge has high heat value, and is especially suitable for incineration disposition.