First of all you should have at least five party pokemon with you and about 20 ultra balls ,,,now get groudons health verry low and when you throw your first ball make shure you hold down L , R , A , B and the down button keep throwing till you catch him i did that and i caught him with a pokeball!

You must have a Master Ball to Capture Groudon. Like it says, The ball without fail. But it's hard to find!

do not use the master ball on groudon or kyoger later on in the game you come across rayquaza and latios and lotias use the master ball on latios or latas its lamost imposible to catch latios or latias with ultra\great\poke\timer\net balls

you can catsch it whit a masterball