A　highly　sensitive　laser-induced　fluorescence　detection　system　with　real-time　imaging　focusing　instead　of　the　use　of　fluorescent　reagents　were　developed　for　the　detection　of　analytes　in　nanocapillaries.　A　cylindrical　lens　was　adopted　for　the　shaping　of　a　laser　beam　to　increase　its　spatial　resolution.　The　limit　of　detection　with　a　capillary　having　a　radius　of　440　nm　was　6.76　yoctomoles　(or　four　molecules)　for　fluorescein,　and　84.5　yoctomoles　(or　51　molecules)　for　FAM-labeled　Hsa-miR-17.　The　designed　system　exhibited　high　sensitivity　and　stability　for　femtoliters　of　sample　and　was　hence　indicated　to　be　suitable　for　analyses　of　single　cells.