With　the　development　of　the　Internet,　a　large　number　of　computer　applications　have　emerged,　and　the　quantity　is　still　growing　rapidly.　These　applications　contain　a　lot　of　useful　data　and　functions,　however,　as　most　of　them　are　not　available　and　couldn＇t　interact　with　each　other,　so　the　data　and　functions　are　difficult　to　shared　and　reused,　resulting　in　a　huge　waste　of　resources.　In　order　to　solve　this　problem,　secondary　development　is　needed　on　the　basis　of　the　source　system.　For　example,　it　is　necessary　to　collect　data　from　client　applications　or　integrate　their　functions.　Therefore,　a　framework　of　automatic　encapsulation　API　based　on　the　client　system　is　proposed　in　this　paper.　Firstly,　using　a　design　pattern　to　reconstruct　the　runtime　software　architecture.　Secondly,　an　algorithm　is　proposed　for　parameter　matching　to　automatically　construct　API　template.　Thirdly,　a　framework　is　implemented　to　support　design　patterns　and　matching　algorithms.　In　conclusion,　we　experimented　with　a　real　client　system,　and　the　results　show　that　in　most　cases　our　method　can　effectively　encapsulate　and　reduce　the　execution　time　of　the　functions.