In　this　paper,　we　report　a　diode　end　pumped　laser　with　a　Yb3+-doped　Ca4GdO(BO3)(3)　crystal　(Yb:GdCOB).　The　dopant　concentration　of　the　crystal　was　7%.　The　crystal　was　pumped　longitudinally　at　976nm　by　a　fiber-coupled　diode　laser.　The　maximum　output　power　of　the　laser　emitted　at　1.055um　was　430mW,　and　the　laser　slope　efficiency　was　75%　with　respect　to　the　absorbed　pump　power.　We　also　observed　that　the　output　power　still　increased　when　the　crystal　no　longer　absorbed　more　pumped　power　(the　crystal　had　been　saturated).　The　possible　reason　may　be　that　the　thermal　lens　effect　changed　the　distribution　of　the　laser　mode.　This　will　be　discussed　in　part　3.