In OLSR, only selected multipoint relays (MPRs) are allowed to forward broadcast data during the flooding process, which reduces the message propagation overhead compared to the classical flooding mechanism. Since every node in a network selects its own MPRs independently, many nodes may be MPRs of other nodes, which results in many collisions in the medium access control (MAC) layer under heavy traffic conditions. In this paper, we propose an MPR candidate selection mechanism for broadcast data aggregation in mobile ad-hoc networks. The proposed MPR candidate selection scheme can reduce the number of MPR candidates and appropriately spread MPR candidates over the whole network area. The performance of the proposed MPR candidate selection mechanism is investigated via mathematical analysis and simulations. We also propose a broadcast data aggregation mechanism to achive efficient resource utilization. Performance evaluation indicates that the proposed MPR candidate selection and broadcast data aggregation mechanism is efficient under heavy broadcast traffic load conditions.