The invention provides a method and a device for determining the performance of a virtual machine. The method comprises the following steps: periodically collecting network bandwidth according to a time sequence; according to the collected network bandwidth, recording time consumed for opening a file on the virtual machine; and according to the recorded time consumed for opening the file on the virtual machine, determining the performance of the virtual machine. Through the method, the problem of low accuracy of the performance test of the virtual machine in the prior art is solved so as to achieve an effect on improving the accuracy of the performance test of the virtual machine.