A styrylpyrylium salt (DHSP) was synthesized and then photodimerized to obtain a cyclobutane-type dimer (DHSP dimer). Methacryloyl group was incorporated into DHSP dimer to obtain DMSP dimer. Based on FT-IR analysis of a crosslinked DMSP dimer, it was considered that the cyclobutane structure reversed to styryl C=C bonds upon crack formation. Fluorescence measurement of DHSP in solid state (excitation at 385 nm) showed emission centered at 626 nm, while DHSP dimer revealed very weak emission. Fluorescent emission from microcracks in a film of crosslinked DMSP dimer was observed upon exposure to $330{sim}385;nm$ light.