A new liquid malononitrile derivative (LBDBP) has been synthesized by incorporating four tetraethylene glycol groups into the prototype scaffold of 2-[Bis-(4′-diethylamino-biphenyl-4-yl)-methylene]-malononitrile (BDBP). The linear photophysical properties, optical/thermal stabilities and optical limiting behaviors of LBDBP and BDBP have been investigated. The results show that LBDBP has equivalent optical/thermal stability but much better solubility compared with BDBP. Its saturation concentration in DMF is increased to 0.075 M, while the corresponding datum for BDBP is only 0.01 M. The improved solubility of LBDBPinsures a very significant optical limiting behavior. The saturated DMF solution of LBDBPcan significantly reduce the intensity fluctuation of laser pulses in an 800 nm laser setup.