(1) A new method for the synthesis of benzylidene acetone with near critical water as reaction media was developed.

(2) The conversion of benzaldehyde and yield of benzylidene acetone were influenced by reaction time, temperature and initial water volume.

(3) Absorption spectra of three novel coumarin sensitizer incorporate benzylidene cyclopentanone moiety were studied.

(4) The yield of benzylidene acetophenone reached 31.4% under optimal conditions.

(5) This paper studies that TLC technology is applied to synthesis of benzylidene acetone. Through TLC is employed to monitor the synthesis process, The ability to analyse and solve problems is enhance.