A multilayer polymer thin film electroluminescence (EL) device has been prepared by fully using the LB film method. We synthesized a novel polythiophene derivative poly-3-(2-(5-chlorobenzotriazole)ethyl) thiophene (PCBET) and studied the EL effect of LB LEDs PCBET as the emitting materials. The PL spectra of polymer shows a peak at around 605 nm, which is about 65 nm blue shifted compared with poly 3-decylthiophene results from the benzotrizole group.