Wireless Sensor Networks (WSNs) consists of small nodes with sensing, computation, and communications capabilities. Protocols for routing, power management, and data aggregation have been designed for WSNs, where energy efficiency is an essential design issue. The most important feature of a routing protocol, for efficiency management is the energy consumption of the network’s lifetime. During the recent years, many energy conserving routing protocols have been proposed for WSNs. This paper consists of Classification and comparison of routing protocols.