Photopolymers containing carboxyl groups as water soluble groups and o , m or p -nitro substituted benzalacetophenone ( o -BAp·NO₂, m -BAp·NO₂, p -BAp·NO₂) as sensitive groups are synthesized by condensing 4-(vinylbenzyloxy) acetophenone-co-methacryic acid copolymer with o , m or p -nitro substituted benzaldehyde in alkaline catalyzer. These condensation polymers were effectively crosslinked by the irradiation of UV light. Alkaline aqueous developing solution available commercially for negative type presensitized plate can be applied for development of these photopolymers. Relative sensitivities of the condensation polymers in film state were measured. It is found that order of sensitivity of the synthesized polymers are o -BAp·NO₂< m -BAp·NO₂< p -BAp·NO₂. The spectral sensitivities of p -BAp·NO₂ were observed to be 0.03-0.05 mJ/cm² at 300-400 nm respectively.