Contour mas are an effective tool to show the spatial distribution of a variable, which is used widely in many fields including meteorology. A contourrelated algorithm class library named “wContour.dll” was developed using VB.NET, which has such functions as interpolation, contour generation, smoothing, clipping, and color filling. The algorithms have been tested with random data, and can be used flexibly in software development to realize contour functions. The contour filling algorithm is based on topology relationship, so vector polygon shapes can be generated. The class library (wContour.dll) could be downloaded and used for free.