Polyphosphoramide esters containing a photo-sensitive bisbenzylidene group in the main chain were synthesized from 2,7-bis(4-hydroxy-3-methoxybenzylidene) cycloheptanone with various N-arylphosphoramidic dichlorides by interfacial polycondensation using a phase transfer catalyst. The structure of the polymers was confirmed by infra-red and H-1, C-13 and P-31 nuclear magnetic resonance spectroscopy. The molecular weights were determined by gel permeation chromatography, and the thermal stabilities were evaluated by thermogravimetric analysis and differential scanning calorimetry. The photo-crosslinking property of these polymers was studied by ultraviolet spectroscopy. The crosslinking proceeds via 2 pi + 2 pi cycloaddition reaction of the benzylidene group. The substitution on the pendant phenyl group has no significant effect on the rate of crosslinking.