The work is aims to establish an optimal design method of vacuum molded composite tank under internal pressure specifically for storage of LPG. In this geodesic path equation was used to calculate the variable thickness of the dome portions, instead of constant thickness throughout the structures. The head shape is obtained by the numerical solution of the elliptical integral. The finite element analysis was performed to identity of safest design cylindrical and dome portion of the structure. The stagnation of fiber matrix composite leads to the variable thickness dome. The experimental test of leak proof and the pressure test also carried out and the results also investigated.