Tension leg platforms are compliant structures for oil extraction in deep water consisting of hull, deck foundation, tendons and risers. The hull is very important part of a TLP from functionality, weight and cost point of views that is made of vertical column and horizontal pontoon with circular and rectangular sections. The hull geometry plays very important rule in optimum action of the structure. The ratio of columns volume to total volume ( ), that is the function of pontoon length ( ), column length ( ), pontoon diameter ( ), column diameter ( ), is an important parameter in structure response against waves loading. In the present research a parametric study has been carried out to investigate the effect of hull geometry on TLP’s responses under wave attack. A wide range of geometric parameters have been considered. A number of models have been set up by changing pontoon length, column length, pontoon diameter and column diameter. In these models the displacement volume, total volume and tendons’ tension were kept constant. Then the structural models were analyzed under wave load using a finite element software. In this paper, results of this parametric study is presented and discussed. Based on these results, appropriate range of dimensionless geometry parameters are proposed for conceptual design of TLPs hull.