NSW skipper Katich and Clarke shared an unbroken 193-run third-wicket partnership against an under-strength SA attack to leave NSW at 338-2 at stumps on Tuesday, answering critics who have called for their Test spots to be reviewed.
Clarke, whose promotion to number four in the Test line-up has been criticised by some high-profile pundits, scored 115 not out from 170 balls with 13 fours and one six.
Katich, who was told by selectors that it was "time to deliver" after averaging 27.55 in the recent Ashes series, hit 16 fours and faced 246 balls for his unbeaten 139.
Katich, who made 0 and 2 and suffered a fractured finger in last week's Super Test against the World XI, needed a big score today with selectors due to announce the team on Thursday for the November 3-7 Test against West Indies in Brisbane.
NSW left-handed opener Phil Jaques hit eight fours and one six in his 104-ball knock before he was out after lunch.
The South Australian attack was missing injured Test duo Jason Gillespie and Shaun Tait.