Digital Terrain Modeling, the Triangulated Irregular Network (TIN) is a representation of a surface derived from irregularly spaced sample points and break line features. Paper deals with the basic concept of Delauney’s triangulation method with its practical approach in ArcGIS. The next section describes the process to convert mass points to TIN model and explores some of the basics of TIN Model with their data structure. The last section gives clear idea about its advantages and disadvantages over grid based model.