We propose an idle probability-based broadcasting method,iPro, which employs an adaptive probabilistic mechanism to improve performance of data broadcasting over dense wireless ad hoc networks. In multisource one-hop broadcast scenarios, the modeling and simulation results of the proposediProare shown to significantly outperform the standard IEEE 802.11 under saturated condition. Moreover, the results also show that without estimating the number of competing nodes and changing the contention window size, the performance of the proposediProcan still approach the theoretical bound. We further applyiProto multihop broadcasting scenarios, and the experiment results show that within the same elapsed time after the broadcasting, the proposediProhas significantly higher Packet-Delivery Ratios (PDR) than traditional methods.