In this study, the polar inertia momentim of the trajectory curve (X) generated by a fixed point X of the moving plane under the 1-parameter closed planar homothetic motion is calculated. And it is seen that ali the fixed points of the moving plane the trajectory curves of which have equal polar inertia momentum lie on the same circle of the moving plane such that the çenter of the circle is generally different from the Steiner point (Theorem 1). Obtaining a a formula which is analogoue of Holditch formula from that we get some corollaries (Corol- laries 3, 4 and 5). Moreover we have given a relation between the areas of orbits and the polar inertia momentums of them (Theorem 2