The invention provides a wafer-level packaging structure and a preparation method thereof. The method herein includes the following steps: 1. providing a wafer which is provided with a semiconductor structure therein; 2. forming a redistribution layer on the upper surface of the wafer, and subjecting the obtained structure to low temperature processing for a preset time period in the process of forming the redistribution layer or after the formation of the redistribution layer until the obtained structure returns to room temperature; and 3. forming metal layer and under bumping on the upper surface of the redistribution layer. According to the invention, the method herein by subjecting the obtained structure to low temperature processing in the process of forming the redistribution layer or after the formation of the redistribution layer, can release strain which is generated in the packaging process, can effectively reduce warping of the wafer which is brought in high temperature curing, with minimum cost, increases precision and operability in the preparation process, and further increases the reliability of components; also, allows the embedding of other passive devices in the package structure.