The objective of this research is to develop the CAD system package used for digitized pattern designs and nesting, based on the mathematical and computational principles. In the pattern generation step, the digitizer is used for completed pattern input and the patterns information is defined such as family, name, size, loop, notch, hole, grading rule and etc. First of all, the geometric and alphanumeric data are defined, and then Qubic Bezier Curve is used in order to obtain the 2-dimensional smooth curve. So all of the pattern information organize the pattern database. After accomplished the step of the drafting patterns, this CAD package coverts the pattern data into the grid pattern data, which organizies the grid-pattern database. So in this research, the grid algorithm is developed. Using the grid algorithm, the overlapping between the patterns is easily protected. The transformation sub-programs easily support the nesting process, used to change the image on the display screen and to reposition the items in the pattern data base. This sub-program, which is applied to the pattern data in order to nest the minimum arrangement, is composed of translation, magnification, reduction, rutation and separation. Therefore, this CAD system package is the total procedures by which the sequence of processing steps to involve drafting clothing patterns, modifications, grading and nesting is planed and carried out. In the operation of this CAD package by the user, every programs is mutually joined.