The invention discloses cement clinker and a preparation process thereof, belongs to the technical field of cement and a preparation process thereof, and aims to solve the problem of providing cement clinker prepared by a waste industrial raw material and a process for preparing the cement clinker. The invention adopts a technical scheme as follows: the cement clinker is formed by the following components in percentage by weight: 56.47-80.75% of limestone, 6.37-18.92% of sandstone power, 7.45-20.28% of magnesium slag, 2.36-8.69% of slack coal ash, and 1.54-6.75% of copper ore slag. The preparation process of the cement clinker comprises the following steps: Step I, collecting the limestone, the sandstone power, the magnesium slag, the slack coal ash and the copper ore slag, and mixing the limestone, the sandstone power, the magnesium slag, the slack coal ash and the copper ore slag according to the set weight percent; Step II, drying and grinding the limestone, the sandstone power, the magnesium slag, the slack coal ash and the copper ore slag mixed in the Step I, and obtaining crude material power; Step III, burning the crude material power obtained in the Step II, and obtaining the cement clinker. The preparation process is applied to cement production.