Bonds lined a 1-1 pitch off Ricky Stone in the ninth inning over the right-center field wall to tie the record for most home runs in a season.
The San Francisco Giants won 10-2, completing a three-game sweep that kept them two games behind Arizona in the NL West race with three games remaining, all against Los Angeles.
Mark McGwire of the St Louis Cardinals hit 70 homers in 1998. McGwire's 69th and 70th came on the final day of the season.
Bonds has now hit 564 home runs, moving him to seventh on the all-time list.
McGwire, who has been battling injury this season, is fifth on the list with 582 home runs.
His San Francisco teammates poured out to greet a smiling Bonds at home plate along with Bonds' son, Nikolai. Bonds pointed at his family behind the third-base dugout as he returned to the bench.
With fans still cheering at Enron Field, he came out for two curtain calls. Bonds took his position in left field to start the bottom of the ninth, was mobbed by teammates who were in the Giants bullpen, then was replaced and left waving his cap.
Bonds' 70th homer marked the second big achievement of the day in the majors. Earlier, Rickey Henderson of San Diego scored his 2,246th career run and broke Ty Cobb's record.
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