The third-order nonlinear optical susceptibilities of $eta$-carotene, retinal and retinol have been measured using self-induced ellipse rotation and dc-Kerr effects. The strengths of $chi$1221(-$omega$, $omega$, -$omega$, $omega$) and $chi$1221(-$omega$, $omega$, 0, 0) measured by the two different methods are not different each other significantly. And it is observed that the strength of the third order nonlinear optical susceptibility is relatively insensitive to the conformational difference between retinal and retinol. It is also demonstrated that the third order nonlinear optical susceptibility of long-chained organic molecules is dependent upon the number of the double-bonds.