Hendry, who dubbed Harold his bogey-man after losing to him on four occasions in nine meetings, made several sizeable breaks during a confident quarter- final performance.
"Dave is one of those players who makes it very tough and so this is a good win for me," he said. "I wasn't looking forward to the match but you just have to get through it whoever you're playing.
"It's nice to win but I would say that there is definitely still room for improvement."
Hendry, who now meets the winner of the last-eight meeting between the Welshmen Mark Williams and Darren Morgan, recovered from 2-1 down to lead 5-2 by knocking in breaks of 96, 72, 116 and 92 during a purple patch of high-quality scoring.
Harold, a semi-finalist in the tournament last year, made 87 in the eighth to make it 5-3 and claimed the ninth frame to close the gap to just one frame.
At 6-4, Harold made 70 to get within one frame once again but the crucial frame proved to be the 12th, which Hendry took after Harold missed the brown and Hendry cleared the last four colours to steal a 7-5 lead on the black.