We tested DfuSe Demo v3.06, but it cannot find our STM32F04 (nothing can be fund). We checked the driver, USB serial device COM12 can be seen. However, STM32 ST-linke can work. Its driver is STMMicroelectronic STLink virtual COM port COM8.

[Tesla DeLorean]

DfuSe demo doesn't use the serial port on the ST-LINK. It needs a USB connection directly​ to the target device, and DFU support in ROM.

[WLi.1]

On windows 10, It is always auto fund in serial port. How can we solve this?

[Tesla DeLorean]

Ok, but finding the ST-LINK serial port helps how exactly?

Why are you using DfuSe Demo? Wouldn't STM32 Cube Programmer or Flash Demostrator be more appropriate?

Question also seriously lacking in contextual detail. What board? Custom? What modes of connectivity does it provide to the outside world? A schematic or system diagram would transcend language issues.

Check USB support in the boot loader for the "STM32F04" in app note AN2606

[WLi.1]

Ok, but finding the ST-LINK serial port helps how exactly?
ST-LINK works fine. It is used for firmware download via JTAG; It is through USB-COM port.
Why are you using DfuSe Demo? Wouldn't STM32 Cube Programmer or Flash Demostrator be more appropriate?
Our target is through USB to upgrade STM32F04. We used DfuSe Demo on windows before, But it does not work now. Can STM32 Cube Programmer or Flash Demostrator be through USB to firmware upgrade?
Question also seriously lacking in contextual detail. What board? Custom? What modes of connectivity does it provide to the outside world? A schematic or system diagram would transcend language issues.
Our board is Custom, outside connection is USB. We also have STM32F407 VG development board to download firmware. We have been using our schematic/ system diagram for more than 2 years. It works fine.
Check USB support in the boot loader for the "STM32F407" in app note AN2606
Our problem is it auto go to COM port when connected, STM driver is not in using. We cannot find the solution in AN2606.

[Tesla DeLorean]

Ok, so an STM32F407

Yes, the STM32 Cube Programmer​ supports USB/DFU and COM/USART connectivity. It is a tool replacing at least 3 older tools.

[WLi.1]

We tried STM32 Cube Programmer , it works. Thank you so much.