[FGSW-PoE] My device do not need PoE power, do I have to turn off the PoE function?

No, the FGSW-2402PVS / FGSW-2620PVS can auto detect the connected devices and decide whether to provide power or not. If the device is an IEEE 802.3af compliant device, the FGSW-2402PVS / FGSW-2620PVS will auto provide 48VDC power on it. If not, the FGSW-2402PVS / FGSW-2620PVS will not provide any power and still work as a managed switch as well.