根据《Regulations of the UEFA Champions League 2011/12》,不清零。
22.02 In case of repeated cautions:
b) from the first match in the group stage, a player is suspended for the next
competition match after three cautions in three different matches, as well
as following any subsequent odd-numbered caution (fifth, seventh, ninth,
etc.).
22.05 Cautions and pending yellow-card suspensions from club competition
matches expire at the end of the season.