Although many efforts have been devoted to encapsulate potential cargo substances with large molecular weights, at present it is still a challenging task to seal small molecules in multilayer capsule cavities. In this work, single-component polyelectrolyte microcapsules based on diazo-resin are proposed to solve this problem. Generally, the multilayer capsule system is built up with DAR polymers carrying both positive and negative charges. Upon exposure to a 380 nm UV light, photolysis between paired diazonium and diazo-sulfonate groups rapidly converts the electrostatic interactions into covalent cross-linking within the multilayer shells. This photo-driven reaction offers an externally controlled method to seal the multilayer capsules. The resulting phenyl-ring-rich shell structures serve as excellent sealed micro-containers to entrap small molecule rhodamine B.