||Conjugated polymers (CPs) were used for electronic devices, such as light emitting diodes, photovoltaic cells and fluorescent sensor because they have a high signal amplification ability compared with that of corresponding monomer. However, CPs are only soluble in organic solvents, because they are commonly a hydrophobic in nature. This feature limited the application of CPs. As an alternative, water-soluble conjugated polymers (WSCPs) with charged groups have attracted much attention for electronic devices in aqueous solution. The detection of important biological thiols such as cysteine (Cys) is highly relevant to a variety of fundamental physiological processes in organisms. Herein, we synthesized novel anionic conjugated polymer containing triphenylamine. In addition, the selective reaction of the aldehyde group with N-terminal cysteines can form thiazolidines. As a result, emission shift of WSCP observed yellow to blue in the solid state.