It's not clear what you mean by "mainframe emulator." I am aware of three.
- PC/370 - This is essentially defunct; it is a 16-bit MSDOS program that will not run under Windoze Vista and more recent versions of Windoze. It has been replaced by
- z390. z390 is Java and should run under current versions of Windoze.
- Hercules is a much more interesting emulator. In addition to Hercules you must also obtain an operating system. Hercules + an operating system is a much more difficult task for a neophyte.
None of these have anything to do with Fandezhi. This forum does not support them.
Perhaps you really mean a TN3270 program that emulates an IBM 3270 terminal that you need to connect to Fandezhi. There are several mentioned in the Mainframe FAQ section of this forum. Look there. Or use Google or M$ Bing to find other options. Most of these programs are not free, though most provide a trial version you can use for a limited time.