The invention provides a QLED device with an enhanced composite structure and a preparation method of the QLED device. The light emitting efficiency of a positive QLED device is improved through a micro-nano structure composite structure constructed by a nano grid structure composite folded structure. The composite structure is constructed on the basis of the nanoimprint technology, the micro-attachment technology and the surface plasma etching technology, and the method comprises the steps: preparing a nanoimprint template and processing the transferred pattern again. An IPS polymer is used as a nano-imprinting template through the nano-imprinting technology, and the template pattern is transferred to the PDMS dielectric layer through the micro-attachment technology; on the basis, the composite structure is constructed on the glass substrate through the surface plasma etching technology to enhance light emitting of the QLED substrate. The QLED device with the enhanced composite structure can have the highest brightness and efficiency, and the brightness and the EQE are improved by 46% at most compared with conventional devices; and the construction mode of the composite structureis simple, the cost is low, and industrial popularization and application are facilitated.