A　new　method　of　measuring　elastic　constants　of　limited-size　materials　is　presented　in　this　paper.　The　measurement　is　based　on　acoustic　microscope　technology.　The　material　elastic　constants　are　determined　by　measuring　longitudinal　wave　and　leak　surface　wave　velocity　simultaneously　by　the　system　with　a　line-focus　PVDF　transducer　developed　by　ourselves.　Based　on　the　virtual　instrument　technology,　a　set　of　precise　measure　software　was　programmed.　Experimental　tests　on　three　limited-size　samples,　aluminum,　cuprum　and　steel,　were　carried　out　using　the　line-focus　PVDF　transducers　and　automatically　measure　software.　The　experimental　results　indicate　that　the　ultrasonic　measurement　system　can　be　used　to　determine　the　elastic　constants　of　limited-size　materials　accurately.　The　main　factors　to　affect　the　precision　of　elastic　constants　were　discussed,　including　the　measuring　error　of　defocus　distance,　thickness　and　time　interval.　Take　Young＇s　modulus　of　aluminum　for　an　example,　the　qualitative　analysis　of　the　errors　sources　influence　on　the　measure　system　was　made.　This　method　is　suitable　not　only　to　measuring　elastic　constants　of　isotropy　materials,　but　also　those　of　anisotropic　ones.