A fault tolerance method and system for a virtual machine group is proposed. The method includes: establishing fault tolerance backup connections of virtual machines between a virtual machine hypervisor of at least one primary host and a virtual machine hypervisor of at least one backup host to perform fault tolerance backups of the virtual machines, wherein the plurality of virtual machines are included in a fault tolerance group; when a synchronizer determines that a failover of at least one first virtual machine among the primary virtual machines in the fault tolerance group is being performed. Informing, by the synchronizer, to perform a failover of other remaining primary virtual machines among the primary virtual machines in the fault tolerance group, or to return other remaining primary virtual machines among the primary virtual machines in the fault tolerance group back to a last fault tolerance backup state of each and continue performing fault tolerance backups of the other remaining primary virtual machines.