A novel hydrophilic polymer based on hydroxyl group grafted onto the side chain of polymer was successfully synthesized. Due to the hydrophilic of hydroxyl groups, the hydrophilic polymer overcame the drawback of fluorescent conjugated polymer insoluble in water. Polymer chains evenly distributed in aqueous solution and possessed the signal amplification effect in the aqueous phase. The hydroxyl groups in polymer could effectively absorb nitroaromatics (NACs) by hydrogen bonding interaction between NACs and hydroxyl groups. When the TNT and DNT concentration was 1.08×10−4mol/L and 1.44×10−4mol/L respectively, the quenching efficiency (ηEP) of polymer reached 93% and 91%. The limit of detection of the polymer to DNT and TNT solution are 7.4×10−7mol/L and 1.1×10−6mol/L, respectively. Fluorescence quenching studies demonstrated that the hydrophilic polymer was highly sensitive towards NACs. Moreover, the excellent property of selectivity indicated the hydrophilic polymer might be a promising sensor in the monitoring field of the underwater hidden explosives and water environmental quality.