Poly3-[4-(4-pentyl-cyclohexyl)-phenyl]-thiophene(P3PhChPeT) films have been electrochemically synthesized by direct oxidation of 3PhChPeT in the mixed electrolyte of boron thrifluoride diethyl etherate(BFEE) and ethyl ether(EE)(4∶1,by volume).The oxidation potential of the monomer was measured to be 1.1 V(versus Ag/AgCl).P3PhChPeT in dedoped state is soluble in usual organic solvents such as tetrahydrofuran and chloroform,etc.The structure of the polymer films was studied by infrared,Raman and UV-visible spectroscopies.The molar mass of the polymer was measured to be about 3400 g/mol with polydispersity of 1.23. The fluorescent spectra showed a single broad band at 566 nm with excitation at 450 nm.The thermal analysis result indicated that this polymer had a high thermal stability with a decomposition temperature higher than 500℃.