This paper introduces two methods for selecting proper ways to fit curves using listing discrete points according to actual needs and the smooth join between curves have been realized by using spline as transition.

On the basis of the problem of drawing intersecting lines in engineering design with computer drawing software, this paper brings forward the use of the spline function and formula curve function by computer drawing software and the method of drawing intersecting lines.

Based on Autodesk Inventor Professional 2009,the paper introduces some basal methods to control and edit the spline,such as geometric constrains, dimensional constraint,changing and restricting the parameter of control points, increasing or reducing the control points, fitting curve, changing the tensity of curve etc.