it always detect as "unknown device"
What says it is an "unknown" device? If you are talking about the USBDock program (or the USB widget, which uses the same data), that is probably true. It says the same for about 90% of USB devices. That means nothing, other than nobody has put the device in the database. As long as it shows the device, it is "seen". To be used, it needs a driver.
I know nothing about the device that you are talking about. If it simply "keys in the data", the keyboard driver should handle it (I assume that the keyboard part works), although it may be necessary to tell the keyboard to use the keys from the reader (which eCS would have no idea how to do). If it is just a sub device of the keyboard, you will need to have a driver that will handle it. The data in the USBDock program, might shed some light on exactly what it is, that you are dealing with.
You may find some clues, if you look up how to use Bar Code readers with OS/2. I would think that it would be similar.
There is a thing called USB Extended Control Driver:
http://hobbes.nmsu.edu/download/pub/os2/system/drivers/misc/usbecd20.zip, which gives you an interface to "unknown" USB devices. That might help you develop some REXX (or other programing language) to access the reader.