A method for connecting virtual machines in a cloud system is disclosed, wherein an agent network management service (Network management service, ANMS) process is used for communicating with all switches in the cloud system. When a virtual machine (VM) is created on one of the physical host in the cloud system, the ANMS detects the creation of the new VM, and confirms the virtual local area network (VLAN) the new VM pertained to. Next, determine a nearest boundary point from the new VM in the same VLAN for confirming a shortest connecting route. Lastly, the ANMS informing all switches in the shortest connecting route to set up internal VLAN tags such that new VM establish connection with other VMs in the same VLAN via the shortest connecting route.