The spatial data contain a lot of points. The points consist of geographic coordinates. Representing the spatial data requires many calculating the geographic coordinates. Calculations of the coordinates take much time and reduce the performance. In order to enhance the performance of rendering the spatial data, performance enhancement for rendering the polygon which are in spatial data is needed. In this paper, we present that improving the performance of rendering for polygon by utilizing the scanline algorithm. The scanline algorithm has been widely used for rendering graphics systems. It fills inside of a given polygon. In order to filling the polygon, it requires some calculations and tables for storing the variables. Calculating and sorting the variables reduce the performance. We propose a method which precomputes the variables used by the scanline algorithm. By using proposed method, it can reduce the processed time. Proposed technique can be utilized to zoom in and out the map. We implement the proposed method and perform the experiment with Tiger/Line spatial data. We compare the processing time between scanline algorithm and proposed method.