Abstract: In wireless sensor network, where nodes are power driven by batteries and it is important to prolong the network lifetime by minimize the energy consumption of each node. Thus the choice of optimal transmission power is one of the prime concerns in such network. Optimal transmission power is the minimum power required to sustain the network connectivity while maintain the predetermined maximum tolerable bit error rate (BER). In this paper, optimal transmission power is derived for a WSN deployed based on random topology. In this paper the effect of three fading channel (Rayleigh, rician & shadowing) on optimal transmission power; route BER and energy consumption for successful delivery of data in multihop is studied for such randomly deployment in wireless sensor network.