n this paper, the critical transmitting range for connectivity in wireless ad hoc networks is analyzed. More specifically, we consider the following problem: Assume n nodes, each capable of communicating with nodes within a radius of r. The nods are randomly and uniformly distributed in a d-dimensional region with a side of lengthl. In this paper the critical transmission range in dense and sparse network is studied. The critical transmission range in RWP mobile network and the critical transmission range for k-connectivity are investigated. The results of this paper could be improved the accuracy of ad hoc network which is commonly used to evaluate the performance of ad hoc network protocols.