Privacy-preserving data mining is a research hotspot. Privacy-preserving data mining based on modified quantum genetic algorithm is proposed in the paper. This algorithm is divided into two steps. The quantum genetic algorithm is used in the first step to get the local Bayesian network structure. The secure statistic protocol of oriented edges is used in the algorithm to protect the privacy. The algorithm is proved to be convergent on theory. Some experiments have been done on the algorithm, and the results proved that the algorithm is feasible.