A input/output method is disclosed for performing communications in a virtual machine (VM) environment between a host operating system (OS) and a guest OS. The input/output method includes performing request polling (RP) on an input/output event generated by a guest OS which is driven by a virtual machine (VM), sending an input/output request to a host OS, on which the VM runs. The input/output method further includes performing response waiting polling (RWP) on an input/output completion message generated by the host OS when the input/output event is detected through the RP, and sending an input/output response to the guest OS when the input/output completion message is detected through the RWP. In the method, the RP and the RWP are performed by multiple threads executed on the VM.