The fundamental physical properties of a side-chain type polysiloxane liquid crystalline polymer, which shows a large electrorheological (ER) effect when diluted with poly-dimethylsiloxane (PDMS), were investigated by means of x-ray diffraction and dielectric measurements. From the results of X-ray diffraction it was found that at about 40 degrees C the polymer undergoes a first-order phase transition from the smectic phase to the isotropic phase. A dielectric absorption due to the delta-process was observed, the activation energy was determined to be 81kJ/mol. In addition, a relatively large conductivity was found in this polymer, the apparent activation energy of which is about 93 kJ/mol.