During the study of resistive switching devices, researchers have found that the influence of the insertion layer cannot be ignored. Many reports have confirmed that the appropriate insertion layer can significantly improve the performance of the resistive switching devices. Therefore, in this work, we use magnetron sputtering to fabricate three devices: Cu/MgO/Cu, Cu/MgO/MoS₂/Cu and Cu/MoS₂/MgO/Cu. Through the characterization test of each device and the measurement of the I-V curve, it is found that the resistive switching characteristics of the Cu/MgO/Cu device will change greatly after adding an MoS₂ insertion layer. The analysis results show that the inserted MoS₂ layer does not change the main transmission mechanism (space charge limited conduction) of the device, but affects the regulating function of interfacial potential barrier, the effect also is related to the location of MoS₂ inserted into the layer. Among the Cu/MgO/Cu, Cu/MgO/MoS₂/Cu and Cu/MoS₂/MgO/Cu devices, the Cu/MgO/MoS₂/Cu device exhibits a larger switching ratio (about 10³) and a lower reset voltage (about 0.21 V), which can be attributed to the regulation of the interface barrier between MgO and MoS₂. In addition, when the MoS₂ layer is inserted between the bottom electrodes Cu and MgO, the leakage current of the device is significantly reduced. Therefore, Cu/MoS₂/MgO/Cu device has the highest commercial value from the point of view of practical applications. Finally, according to the XPS results and XRD results, we establish the conductive filament models for the three devices, and analyze the reasons for the different resistive switching characteristics of the three devices.