In mobile ad hoc networks (MANET), broadcasting is widely used in route discovery and many other network services. The efficiency of broadcasting protocol can affect the performance of the entire network. As such, the simple flooding algorithm aggravates a high number of unnecessary packet rebroadcasts, causing contention and packet collisions. Proper use of probabilistic method can reduce the number of rebroadcasting, therefore reduce the chance of contention and collision among neighbouring nodes. A good probabilistic broadcast protocol can achieve high save rebroadcast and low collision. In this paper, we propose a dynamic probabilistic approach when nodes move according to different mobility models and compare it with simple flooding AODV and fixed probabilistic scheme. Our approach dynamically set the rebroadcast probability according to the number of neighbour nodes distributed in the ad hoc network. Simulation results show our approach performs better than both simple flooding and fixed probabilistic flooding.