A data anonymity method and a data anonymity system are provided. The data anonymity method includes the following steps. A data set comprising a plurality of direct-identifiers, a plurality of quasi-identifiers and a plurality of event logs each of which includes an activity and a timestamp is obtained. A content of each of the direct-identifiers is replaced by a pseudonym. The quasi-identifiers are classified, via a group-by algorithm with k-anonymity, as a plurality of equivalence classes. The activities corresponding to each of the direct-identifiers are linked according to the timestamps to obtain a plurality of event sequences. A similarity hierarchy tree is obtained according to a plurality of edit distances among the event sequences. The event sequences are grouped according to the similarity hierarchy tree with k-anonymity to obtain at least one group. The event sequences which are in the group are generalized.