The triangular subdivision method can maximally retain the original information when generating geochemical contour in the MapGIS automatically, but its surface visual effect is poor and huge finishing workload will be changed later. When Gird generates isoline grid data, there will be a condition that the accumulation centers of elements and the point location of extreme value will change to some extent, and it is not convenient for analysis of the geochemical characteristics and the anomaly verification work in late stage. Based on studies, the author found that if the extremum points in the discrete sampling point analysis data are extracted, buffer is established for the extremum value points according to a certain threshold, through point-to-area spatial analysis, the deformed grid nodes in the regular grid which are relatively close to the extremum points and might affect the triangle subdivision mesh optimization are rejected. After that, the discrete extreme value point data and the regular grid data that have rejected the deformed grid nodes grid data are merged, followed by triangular subdivision contour tracking. These measures satisfactorily make up the shortcomings of the two methods mentioned above. This method does not need using other software tools and only employs the MapGIS. The method can generate geochemical contour of extreme values without deviation, and both the mapping accuracy and the visual effect are fairly good, thus having good practicability.