In order to understand the environmental pollution of surface water caused by road construction in the Plateau Ecological Reserve, and to provide some data basis and support for the construction units to grasp the environmental changes of surface water in a timely manner. Sources of surface water environmental pollution during highway construction were analyzed. The water quality evaluation index factors with targeted pollution characteristics of the plateau ecological reserve were selected. The surface water environment evaluation model based on entropy weight - topological object element theory was established, and the applicability and accuracy of the model were verified in the context of the actual project. The results show these as follows. Six water quality evaluation index factors, such as petroleum, permanganate index, SS, NH₃-N, TP and DO, are selected as the evaluation system, which can comprehensively reflect the impact of the road construction period on the surface water environment of the plateau ecological reserve. In practical engineering application, the grading results obtained from the surface water environment evaluation model based on entropy weight extension matter element theory, and the grading results obtained from the single-factor index method and the gray weighted correlation method agree with 70% and 90%, indicating that the method has certain applicability and accuracy.