Abstract: In the present research influence found that adding Sn2P2S6 (SPS) nanoparticles on the electro optic properties of poly-siloxanes side chain liquid crystal polymers have been studied. The five samples of different spacer length have been used. It is found that switching voltage increases with spacer length increasing. The switching times (on) and (off) have been measured through the period between planer and homotropic alignment which happens under the electrical field effect. The variation of the threshold voltage is measured at constant steps below nematic isotropic transition Temperature (T ) for series of polymers. It is found that NI the high spacer length of polymers have great threshold voltage of the electro-optic response and this is related to the intrinsic elastic constant of the liquid crystal polymers. Infrared dichroism measurements have been used to determine the orientational order parameters of the liquid crystalline side chain polymers. By identifying a certain band (CN stretching) in the infrared absorption spectrum, it is found that the orientational order depends on the temperature with different spacer length. A simple model is used to indicates the origion of the effects of observed which appear to arises from the constraint offered by the coupling of the mesogenic units to the polymer backbone.