A vapor-condensation-assisted optical microscopy system comprises a vapor-condensation-assisted device and an optical microscope. The vapor-condensation-assisted device comprises air blowing device, a vapor producing device and a guide pipe. The vapor producing device connects the air blowing device with the guide pipe. The optical microscope comprises an observing device, an image processing device, a support frame and a stage. The stage, the guide pipe of the vapor-condensation-assisted device, the observing device, and the image processing device are fixed on the support frame. The vapor-condensation-assisted device is configured to provide a vapor to sample on the stage in application.