Vertical　Cavity　Surface　Emitting　Laser(VCSEL)　generally　require　a　beam　shaping　process　before　being　applied　in　various　scenarios　due　to　the　beam　propagation　characteristics.　The　beam　waist　position　and　size　of　the　VCSEL　are　critical　for　beam　shaping,　associated　with　the　injection　current.　In　this　contribution,　the　theoretical　model　of　the　equivalent　confocal　cavity　is　innovatively　employed　to　analyze　the　variation　of　the　beam　waist　size　and　the　position　of　VCSEL.　Concurrently,　a　novel　approach　has　been　proposed　to　investigate　the　variation　of　the　beam　waist　by　measuring　the　wavefront　of　the　beam　transformed　by　a　single　lens.　The　beam　waist　size　is　calculated　by　measuring　the　far-field　divergence　of　the　beam　and　data　reveal　that　the　beam　waist　diameter　decreases　from　3.27　μm　to　1.15　μm.　Combined　with　the　change　of　beam　waist　size,　the　shift　of　the　beam　waist　position　on　the　optical　propagation　axis　is　analyzed　in　micron　level.　At　the　end,　we　calculate　the　optimization　effect　of　this　study　on　the　beam-collimated.　©　2022　SPIE.