Isoline drawing is one of the important methods of environmental factor visualization.According to the distribution characteristics of ocean environmental information such as SST and chlorophyll,which can be obtained in the form of two dimensional matrix,regular triangle network can be directly established and the original isoline can be generated in the triangle network.The module of isoline generating was formulated by the development tool Visual C .In order to smooth the original isolines,new key points were repeatedly appended to erase sharp angles of the isolines with the original value points maintained.Then,the smoothing process was further analyzed and an SST isoline chart drawn by this means was given.At last,the difference between this method and the one used in ArcView was also presented.