The utility model relates to an anti-aging plastic prefabricated combined cistern baulk and belongs to the technical field of land consolidation projects. The cistern ridge comprises a cistern and a baulk body, the cistern is arranged besides a terrace and services as a ridge in an integrally combined manner, and the ridge is arranged on the baulk body; the baulk body comprises one or more than one stacked prefabricated plastic boxes, hollow joints and water passing holes which are corresponded in positions and which can in seamless sleeved connections are arranged in two adjacent boxes respectively, and the boxes are communicated with each others through the hollow joints and the water passing holes and are sealed to outside; the lower portion of the front face of the baulk body is provided with a water discharging pipe and a valve, and a desilting port and a plug are arranged in the lower portion of the water discharging pipe; the plastic surface of the baulk body exposed outside is roughened during prefabrication, concrete or anti-aging material is sprayed onto the surface during construction, and climbing vines are planted at the roots of the ridge and baulk body to cover the exposed surface. The anti-aging plastic prefabricated combined cistern baulk has the advantages that ageing of plastic is mitigated, service life of the cistern baulk is prolonged, and the cistern baulk is convenient to promote and use.