The　thermal　effect　of　gain　medium　is　an　important　factor　to　control　the　high　power　and　high　beam　quality　of　the　grazing　incidence　slab　laser.　The　Nd:　YAG　and　sapphire　crystal　bonding　method　is　used　to　study　the　thermal　effect　of　grazing　incidence　slab　laser.　The　temperature　field　distribution　and　thermal　focal　length　of　gain　media　of　Nd:　YAG　and　sapphire　bonding　crystal　are　simulated　theoretically.　The　output　characteristics　of　gain　media　of　Nd:　YAG　and　sapphire　bonding　crystal　and　single　Nd:　YAG　crystal　are　compared　experimentally.　The　maximum　stable　output　power　of　the　bonding　crystal　is　26%　higher　than　that　of　the　single　Nd:　YAG　crystal,　under　the　same　condition　of　cavity　length　and　pump　free　oscillation.　When　the　pump　power　is　44　W,　the　thermal　focal　length　of　bonding　crystal　increased　by　69%　with　respect　to　the　single　Nd:　YAG　crystal.　The　beam　quality　factors　along　the　width　and　thickness　direction　of　bonding　crystal　are　Mx2=1.84　and　My2=2.29,　respectively.　The　beam　quality　factors　along　the　width　and　thickness　direction　of　single　Nd:　YAG　crystal　are　Mx2=2.92　and　My2=4.38,　respectively.　The　theoretical　analysis　and　experimental　results　show　that　the　Nd:　YAG　and　sapphire　bonding　crystals　can　reduce　the　thermal　effect　of　gain　medium　in　grazing　incidence　slab　laser,　which　is　beneficial　to　improve　the　output　power　and　beam　quality.　©　2017,　Chinese　Lasers　Press.　All　right　reserved.