Stimuli responsive photodynamic therapy (PDT) is a hot topic in precise medicine. However the low abundance of responsive trigger molecules in early-stage diseases limits its application. Here we designed an amplifier with multiple upconversion luminances to achieve near-infrared photo-switched cascade reaction triggered by specific microRNA and precise PDT of early-stage cancers. This amplifier was composed of photo-caged DNA nanocombs and an upconversion nanoparticle (UCNP) sensitized with IRDye® 800CW. The nanocomb was prepared by assembling a “photozipper”-protected hairpin and two kinds of hybridizable hairpin probes on a DNA skeleton. Upon 808-nm light irradiation, the produced UV light cleaved off the “photozipper” to induce microRNA-responsive cascade hybridization reaction, which activated the photosensitizers linked to different hairpins to generate reactive oxygen species (ROS) under the simultaneously emitted blue light for efficient PDT. The in vitro and in vivo results demonstrated the high amplification efficiency and promising application of the photo-switched amplifier in early-stage cancer treatment.© 2020 Wiley-VCH GmbH.