Two　types　of　embedded　microball　lenses　namely　convex　microball　lens　(VMBL)　and　concave　microball　lens　(CMBL)　with　outstanding　optical　properties　were　successfully　fabricated　inside　a　polymethethyl　methacrylate　(PMMA)　substrate　by　utilizing　a　high　repetition　rate　femtosecond　fiber　laser.　The　fabricating　mechanism　of　the　VMBL　was　refractive　index　change　induced　by　femtosecond　laser,　and　the　CMBL　was　fabricated　due　to　the　multiphoton　absorption　and　the　heat　accumulation　effect　of　the　successive　laser　pulses　irradiation　at　a　high　repetition　rate.　As　an　example,　the　CMBL　fabrication　efficiency　with　20×　and　50×　microscopic　objectives　was　compared.　The　principles　for　choosing　a　proper　objective　when　fabricating　customized　embedded　lens　were　also　discussed.　Additionally,　these　lenses　can　be　used　as　powerful　tools　in　constructing　specific　micro-optic　systems　towards　various　applications.　This　technology　also　allows　the　direct　fabrication　of　microlens　inside　microfluidic　devices　to　enhance　the　ability　of　gathering　fluorescence　signals　and　optical　imaging.　It　is　very　possible　to　fabricate　a　function-integrated　microfluidic　chip　in　one-step　by　utilizing　this　technology　in　the　near　future.　©　2015,　Beijing　University　of　Technology.　All　right　reserved.