In　order　to　solve　the　difficulty　for　manufacture　of　micro-lens　in　micro-detector　of　fluorescent　spectrum,　a　new　manufacture　technique　of　micro-lens,　molded　on　needing　position,　was　proposed.　Light　gathering　ability　of　the　optic　micro-lens　was　researched.　Using　principles　of　traditional　geometric　optics,　ray　tracking　equations　of　stimulating　micro-lens　and　detecting　micro-lens　were　derived.　Distributed　probabilities　of　illumination　points　for　the　two　micro-lenses　were　calculated　by　using　these　equations.　Some　corresponding　distributed　curves　were　given.　Influence　of　the　micro-lens＇s　shape　on　the　light　gathering　ability　was　discussed.　Results　indicate　that　the　contact　angle　between　optic　glue　and　glass　base　can　be　decreased　and　the　shape　parameter　of　the　micro-lens　can　be　increased　by　adulteration　in　the　optic　glue　and　milling　the　glass.　It　can　both　strengthen　adhesiveness　between　the　glue　and　the　glass,　and　increase　light　gathering　ability　of　the　micro-lens.　A　micro-detector　for　fluorescent　spectrum　with　micro-lens　molded　on　needing　position　was　manufactured　and　the　biological　fluorescent　reagent　was　measured.　Experiment　results　indicate　that　the　intensity　of　the　biologic　fluorescent　spectrum　can　be　increased　more　than　4　times　by　using　micro-lens　molded　on　needing　position,　the　light　gathering　ability　of　the　micro-lens　can　be　increased　1.2　times　though　adulteration　in　the　glue　and　milling　the　glass.