The invention discloses a load balancing system and a load balancing method in an IaaS (Infrastructure As A Service) cloud environment. Through adding a load balancing scheduling module, periodic adjustment of a load balancer is implemented, so that the problems that although the existing load balancer can distribute the flow and carry out load balancing on a back-end machine, the back-end machine of the load balancer is changed to a virtual machine from the conventional physical machine, and the load balancer cannot make an appropriate load balancing strategy according to the corresponding relation between the virtual machine and the physical machine in order to cause the unbalanced load of the physical machine in the cloud environment can be solved. According to the situations, the load balancing system and the load balancing method guide the load balancer to carry out periodic weight adjustment through combining a cloud environment topology and real-time monitoring information, so that an effect of balancing the load of the physical machine in the cloud environment is achieved.