At the initial design, estimate of key numbers such as resistance, displacement, dead weight, light weight, and so forth is required using only a few parameters (e.g.L, B, D, or Cp). Among these key numbers, full load displacement, cargo hold capacity, rough arrangement and so forth. can be estimated accurately if the hull form is defined. Authors made a prototype 3D CAD system for initial hull form design based on the Pro/ENGINEER with using its customizing module. This system makes use of a template ship consisting of side and bottom flat, bilge circular, bow and stern free surfaces. Users can get a desired ship from the template, modifying the lines between these surfaces and spline surfaces in bow and stern. It can also provide hydrostatic curves, lines and Cp curve of the obtained hull form.