The purpose of the paper is to propose a design procedure for preliminary ship-lines using a high speed digital computer, which derives prismatic curve, offsets and hydrostatic data with which given characteristics are satisfied, from the standard series having block coefficient within the range from 0.65 to 0.85. The method is outlined as follows : - The data of the prismatic curves and lines' offsets of the standard series, which are provided beforehand as basic data, are loaded in the high speed digital computer (I.B.M. 7090 is used in this case) with the object program for the calculation. By these data and object program, the computer calculates and prints out the prismatic curve, offsets and hydrostatic data having given characteristics such as principal dimensions, prismatic coefficient, midship section coefficient, longitudinal centre of buoyancy, sharpness of shoulder of prismatic curve, shape of section of body and sheer. In the first part of the paper, the principles of the method are described. In the second part. the standard series of prismatic curves and lines are illustrated in detail. Finally an outline of the procedure of the calculations of prismatic curve, lines etc. is given, using I.B.M. 7090, and an example is also presented.