In this paper, the authors study and represent various techniques of load balancing in data center using virtual machine migration. Virtual machine migration requires memory, storage, and network connectivity are transferred from overloaded host machine to under loaded destination machine. The main aim of VM migration is to balance the load of physical machines in Cloud environment. This paper focuses on virtual machine allocation in Cloud data center. They have represented various existing load balancing techniques, recent work and recent methods of load balancing. Finally, they have presented challenge issues and future research directions for load balancing in Cloud Environment.