The maximum number of civs, which you can have in a map, is determined by the file CvGameCoreDll.dll. By default it's 18, and without any change in this file, the game will crash if you set more civs on the map.
There should be a CvGameCoreDll.dll in the database available, which allows up to 50 civs (you're not forced to use all the slots ).
i use 40civs dll but thank the help i will try 50 civ dll