An　aspherical　reflecting　focusing　mirror　is　designed　and　applied　to　reflect　and　finally　focus　the　laser　beam　of　a　laser　diodes　stack　into　a　spot,　whose　original　beam　size　in　fast　axis　direction　is　22mm　with　a　divergence　angle　of　0.5　degree,　and　in　slow　axis　direction　is　10mm　with　a　divergence　angle　of　6　degree.　In　addition,　the　beam　transformation　principle　of　passing　through　this　mirror　is　analyzed　theoretically.　The　function　of　mirror　is　validated　by　experiments　showing　that　the　actual　focal　length　is　300mm　and　the　focused　spot　is　an　ellipse　in　shape　whose　major　axis　is　1.2mm　and　shorter　axis　is　1.0mm.