Tremendous interest has been evoked in the utility of the fluorescent conjugated polymers towards the creation of ultra-sensitive systems based on the molecular wire effects which can amplify the transduction events. Here, a series of new polymers ¾ pyridine substitute poly (phenylene ethynylene)s are synthesized by Sonogashira-Hagihara coupling reaction. The impact of structure modification on the physical properties and spectral characteristics of polymers has been investigated. The quenching studies are carried out and exhibit that recognition site (pyridyle group) highly influences the quenching efficiency. The results show that polymer PI with pyridyl group entrapped in the conjugated backbone has the specific and sensitive response to Pd(Ⅱ). The fluorescence quenching of PⅠby Pd(Ⅱ) is about 65 times greater than that of model monomer. Keywords: molecular wire effects, amplification signal, pyridine substitute poly(phenylene ethynylenes), Pd (Ⅱ).