A　microchannel-based　electrochemiluminescence　(ECL)　sensor　was　developed　for　detection　of　tetracycline　(TC)　utilizing　luminol/H2O2　as　ECL　reporting　system.　The　low　excitation　potential　of　luminol/H2O2　effectively　mitigated　the　impact　of　clamping　voltage,　thereby　enhancing　the　detection　performance　of　the　microchannel-based　ECL　sensor.　The　microchannel　modified　with　TC　aptamer　selectively　recognized　and　captured　target　TC.　The　positively　charged　TC　reduced　the　surface　charge　density　within　the　microchannel,　thereby　increasing　the　ionic　current　in　the　microchannel,　leading　to　change　of　ECL　signal　of　system.　The　experimental　conditions　such　as　electrolyte　concentration,　TC-aptamer　concentration,　and　reaction　time　between　TC　and　TC-aptamer　were　optimized.　Under　optimal　conditions,　the　difference　of　ECL　signal　in　the　absence　and　presence　of　TC　(triangle　ECL)　exhibited　a　good　linear　relationship　with　TC　concentration　in　the　range　from　1.00　ng/mL　to　200　ng/mL,　with　a　detection　limit　as　low　as　0.69　ng/mL.　The　sensor　had　good　selectivity　and　was　successfully　used　in　detection　of　TC　in　milk　samples.