In this study, an assembly of stimulus-sensitive gel particles with DNA-dye complexes was investigated for application in optical-sensing devices. This composite material of stimulus-sensitive gels and DNA detects external stimuli as a photo-signal. An assembly of the composite gel particles with DNA-dye complexes would be expected to achieve high responsiveness and to quickly detect environmental information as a photo-signal, because the porous structure produced by its interparticle spaces decreases with the relaxation time of the three-dimensional network structure. Poly(acrylic acid) (PAAc) gel particles with DNA were prepared by emulsion polymerization and the gel particles were assembled by a crosslinking reaction between the gel particles that utilized glutaraldehyde. It was possible to prepare the assembly of PAAc gel particles with DNA in sheet and block shapes by utilizing shaped forms for this synthesis process. The swelling ratio of the assembly increased with the pH, and the assembly reached equilibrium swelling in approximately 180 s. The response speed of the assembly was improved to more than 30 times faster than that of a typical PAAc block gel. Furthermore, the assembly of PAAc gel particles with DNA-ethidium bromide complexes detected pH information in an external solution as an optical signal.