The invention belongs to the technical field of sludge treatment devices and particularly relates to a sludge composite conditioner and a conditioning method using the same. The sludge composite conditioner disclosed by the invention consists of conditioners A, B and C, wherein major components of the conditioners A, B and C are respectively hydrogen peroxide, ferrite and persulfate. The specific conditioning method comprises the following steps: (1), analyzing content of volatile suspended solid (VSS) in sludge, and calculating and respectively weighing/measuring a certain amount of the conditioners A, B and C according to a rule that every gram of VSS needs 1mmol-3mmol of the conditioner A, 1mmol-3mmol of the conditioner B and 1mmol-3mmol of the conditioner C; (2), adding the weighed/measured conditioners A, B and C into the sludge, and carrying out mechanical dehydrating operation onto the sludge after stirring for 1 minute-10 minutes. The method disclosed by the invention is simple, dosage of conditioners is less, cost is low, dehydrating effect is obvious, and sludge moisture content can be lowered to less than 60% from 97%-99%; after being dehydrated, the sludge can be directly filled and buried, applied in agriculture or used for producing building materials, and the like.